the female flowers also are disposed in the same manner; in the other, Cycas, they are placed upon the toothings of abortive leaves, occupying the centre of the terminal bud. The leaves of these plants are pinnated, and have a certain resemblance to those both of ferns and palms; their wood is arranged both in concentric circles, which in Cycas are numerous, and in a confused manner among the central pith; so that a Cycadaceous stem partakes in structure of the peculiarities of both Exogens and Endogens. In the manner in which their leaves unrol, and in their terminal single bud, Cycadace resemble Ferns, with which they may moreover be compared on account of their fruit proceeding from leaves; with Conifere they accord in the conelike arrangement of their parts of fructification and their naked ovules; and with Palms in the secretion of a large quantity of fæcula in their stem, in their mode of growth, and in the arrangement of a part of their woody system. Cyca lace therefore, belonging as they do to Gymnos perms, possess nearly equal affinity with Palms or Endogens, and Tree ferns, or Acrogens.

A few plants inhabiting India, New Holland, the Cape of Good Hope, and tropical America, constitute the whole of this order, all the species of which contain a large quantity of fæcula in their trunk. Cycas circinalis yields a coarse sort of sago in the East Indies, and arrow-root of the finest quality is manufactured from Zamin furfuracea in the West Indies.

CYCLADES. [ARCHIPELAGO, GRECIAN.] CYCLANTHA'CE.E, a highly curious but little known natural order of plants, allied to Pandanacea, from which their habit and fructification distinctly divide them. They have plaited, slit, stalked leaves, and a spadiceous inflores cence like Araceae; the flowers are arranged in spiral bands upon the spadix, one band being alternately male and the other female. The whole order consists of a very small number of tropical American plants. (See Lindley's Natural System of Botany, p. 362.)

(lanthus bipart tus

(cusλog), has an arbitrary use in chronology. Certain of the cycles, or recurring methods of denoting time, which are in common use, are called cycles, to the exclusion of the rest. The principal of these, if not the only ones, a.e the Metonic cycle [METON, CALIPPUS), the SOLAR Cycle, and the cycle of INDICTION. But the natural cycles, such as the revolutions of the sun and moon, are not called cycles; nor even some of the artificial ones, such as the Julian period. It would be useless to retain this artificial and confused distinction. Under the distinctive words METON, INDICTION, &c., the reader will find the origin of each method of reckoning; while in the article PERIOD OF REVOLUTION he will see a table of the length and tu mencements of all the cycles, natural and artificial, whether called cycle, period, year, day, or month.

CYCLICA, a section of coleopterous insects. Acco.dig to Latreille, this group forms a subsection of the ecota Tetramera; the groups Tetramera, as well as Pentame.a. however, we imagine are somewhat artificial. See Cerer

TERA.

The section Cyclica contains the Linna an genera Hits. Cassidu, and Chrysomela, the species of which may be t tinguished by the following characters: - Tarsi four jointed, furnished beneath with a velvet-like subs'ance; the fetultimate joint bilobed; antennæ of moderate length, geerally filiform, or increasing in thickness towards the apex: body usually of a rounded or oval form, the thorax beg at the base of the same width as the elytra.

These insects are usually of brilliant metallic cloureng various shades of green appear to predominate. Ther larvæ have a soft body, and are furnished with six legs, attached two to each of the three first segments, or the-e next the head. They feed upon the leaves of plants.

To this group belong the following families:-Cass ada, Chrysomelidae, and Galerucida. The princl genera belonging to the family Cassidiada are, Alur, Hispa, Chalepus, and Cassida. To these genera we shall at present confine our remarks, commencing with the g. nus Cassida, the technical characters of which are:-Body oval or rounded, depressed; thorax generally somewhat semicircular, with the anterior portion produced so as to conceal the head; mandibles with three notches on the inner edge; external lobe of the maxilla as long as the inner one.

The Cassida are usually of a somewhat flattened forta, and are remarkable for their having the external margins of the elytra projecting beyond the body; the outer margins of the thorax are also produced, and conceal the head. Those parts which extend beyond the animal itself are generally semitransparent and flattened, whilst the parts which immediately cover the insect are more or less cultex When the insect is at rest, the legs, which are rather start and compressed, are retracted, and the external margins of the elytra and thorax are applied closely to the plant en which it lives. The larvae of the Cassidue are of a depressed form, and usually armed on the upper parts with numerous little spines; these are longest on the sides of the body and at the tail. The use of these little spines appears to Le for the purpose of holding the excrement of the anim.1, w!. h is always deposited upon its back, and probably serves as a means of defence, by concealing it from its enemies

Cassida viridis, an insect not uncommon in this country, is about a quarter of an inch in length, and of a bright green colour above; the body beneath is black. This species lives both in the larva and imago states upon thistles

Mr. Stephens, in his Catalogue of British Insects, enumerates nineteen species of this genus.

The insects belonging to the other three genera of the Cassidiada have the body of a more elongated form thas those just described, and the head is exposed, the marg.n of the thorax and elytra no: being produced. They are all included in the genus Hispa of Linnæus.

CYCLOBRANCHIANS. (Cuv.) [CYCLOBRANCHIATA CERVICOBRANCHIATA.]

CYCLOBRANCHIATA.

M. De Blainville's hard

order of the second section of his subclass Paracephalophora

monoica.

juntil an caure spada.

CYCLAS. [VENERIDE]

CYCLE. This term, which means nothing but circle

posterior part of the body. Skin naked, and more or les tuberculous. (De Blainville.)

The characters of these families are given under their proper heads

Genera Doris.*

Body oval, more or less depressed; the borders of the mantle going beyond the foot and head on all sides. Four tentacula, two of which are superior and contractile within a cavity, and two inferior under the border of the mantle. Mouth at the extremity of a small fleshy tube, without teeth, but with a lingual mass beset with denticles of some size. Branchia ramified, or in form of projecting foliated branches, disposed in a circle more or less complete in front of the vent. Organs of generation terminating on the anterior part of the right side in a common tubercle.

overpassed throughout its circumference by tne porders of the mantle. Four tentacula as in Doris, besides the labial Organs of respiration formed by very small appendages. ramifications, disposed circularly, and contained in a cavity situated at the posterior and mesial part of the back. Vent mesial at the inferior and posterior part of the border of the mantle. Orifices of the organs of generation very distant, and united by an external furrow occupying the entire length of the right side. Example, Onchidoris Leachii.

[Onchidoris Leachii.]

a, side view; b, seen from below.

M. De Blainville established this genus for a mollusk in the British Museum, the locality of which was unknown. Peronia.

Body suboval, tumefied above. Foot oval, thick, overpassed throughout its circumference by the borders of the mantle. Two inferior tentacula only, depressed, and but little contractile, and two labial appendages. Respiratory organ nearly retiform or pulmonary, in a cavity situated at the posterior region of the back, and opening externally by a rounded mesial orifice, pierced at the inferior and posterior part of the borders of the mantle. Vent mesial, situated in front of the pulmonary orifice. Orifices of the organs of generation very distant; that of the ovary entirely at the posterior extremity of the right side, continued by a furrow to the root of the labial appendage of that side: orifice of the exciting organ very large, nearly mesial at the anterior part of the root of the tentacle of the same side. Example, Peronia Mauritiana.

a

!Peronta Mauritiana.j

a, side view; b, seen from below.

M. De Blainville observes, that this genus contains the marine Onchidia of Cuvier, and that he knows of four or five species, all from the southern hemisphere.

N. B. The Cyclobranches, Cyclobranchians of Cuvier, form the eighth order of Gastropods of that zoologist, and contain the genera Patella, Linn., and Chiton, Linn. CERVICOBRANCHIATA, vol. vi., p. 440 et seq.; CHITONS, vol. vii., p. 94 et seq.

CYCLOID (KUKλosong, like a circle), a name very incorrectly given to the curve which is traced out by any point of a circle rolling on a straight line. Thus while the wheel of a carriage revolves, each nail on the circumference describes a succession of cycloids. We might also here describe the various curves made by the points of circles which roll inside or outside of other circles, &c. &c. But as the cycloid stands apart from all the rest, both in simplicity and historical notoriety, we shall here confine ourselves to this one curve alone, and refer the rest to the head TROCHOIDAL CURVES.

If we suppose a circle to roll on a straight line, it is obvious that the centre will advance in every moment through a length equal to the portion of the circumference which is brought in contact with the line on which the circle rolls. That is,

VOL. VIII.-2 K

Supposing C, the point now highest on the circle, to be the one whose path is to be traced, then, by the time the mere rotation would have brought this point to P, the whole system will have been carried forward through a length PQ equal to the arc CP. Hence follows a very simple mode of con ceiving the form of a cycloid at every point P imagine a line PQ parallel to AB and equal to the arc CP; the extremities of all these lines will be in the cycloid. The are AC, through which the point on the circle rises from the line AB to its highest position, is similar and equal to the arc CB through which it descends. In the diagram we see small parts of the preceding and succeeding cycloids.

The principal properties of the cycloid are as follows:1. PQ is equal in length to the arc CP.

2. The tangent at Q is parallel to the chord CP.

3. The arc CQ is twice the chord CP, and the whole arc ACB is four times CE, the diameter of the generating circle.

4. Complete the rectangle CQR; the area CQR is equal to the circular area CPM, and the whole area ACB is three times that of the generating circle.

5. The curvature at Q is the same as that in a circle whose radius is twice EP, and the involute and evolute (see these terms) of a cycloid are both cycloids of the same magnitude.

6. If the figure be reversed, so that C is the lowest point of the cycloid, and A and B the highest points; then, no friction being supposed, and the cycloid being of resisting matter, a small weight placed at Q will take the same time to slide to C, wherever the point Q may be. Hence all the arcs of the cycloid are said to be synchronous.

7. On the same supposition as in the preceding, a weight will slide from B to Qin a shorter time than in any other curve which can be drawn between B and Q. Hence the cycloid is called the brachystochron.

Let 0 be the angle COP (in theoretical units) [ANGLE], CM = x, MQ = y, OP = a, then we have the following equations:

x = a (1 cos 0) ya (0+ sin 0)

from which the properties of the curve may be deduced.

If, instead of measuring PQ from P, we had carried it forward from M, then Q would have described a curve known by the name of the companion to the cycloid, but which is in truth a curve of sines. [SINES, CURVE OF.]

The history of the cycloid is remarkable from the contests which it produced, and the manner in which the names of Galileo, Descartes, Mersenne, Pascal, Roberval, Wallis, and others, appear in connexion with it. But there would be little use in giving an abstract of history on points of no material use, and the interest of which depends on the light in which a detailed account, and nothing less, would place the state of science of the seventeenth century. Gallileo was certainly the first who attempted the investigation of the properties of the cycloid, as appears from a letter to Torricelli, written in 1639. (See Montucla, Hist. des Math., vol. ii. p. 52, &c.)

CYCLO'LITHĖS. [MADRI PHYLLIEA.]
CYCLOPA'DIA. [DICTIONARY.]

CYCLOPS. (Zoology.) [BRANCHIOPODA, vol. v. p. 340 et seq.]

CYCLO'STOMA. [HELICIDE.]
CYDER. [CIDER.]

CYDNUS. [ANATOLIA; CILICIA.]

CYDO'NIA VULGA'RIS, or QUINCE, of the fruit of which there are two varieties, apple-quince and pear. The seeds are the part used in medicine, on account of the mucilage which they yield. The seeds are more numerous in the small hard than in the large fleshy fruits. They generally occur in large u regularly-shaped masses, as they easily adhere to each other, owing to the mucus which invests them. When moistened the mouth or in water, they give out a large

CYGNUS. [SWAN.] CYLINDER, in mathematics (úvopoç), a name given generally to the surface formed by a straight line which moves parallel to itself, whatever may be the guiding curve; but frequently confined to the common definition, which supposes the straight line to be of finite length, and to move round the circumference of a circle, keeping always at right angles to its plane. We shall extend this a little, and treat of the cylinder which has an oval for its base, and the moving line at right angles to the plane of the base. whence the cylinder is called a right cylinder.

The cylinder may be considered as a cone, of which the apex is at an infinite distance; and many of the general notions in the article CONE may be applied to it.

The content of a cylinder (in cubic units) is the number of square units in the base multiplied by the number of linear units in the altitude. Thus the cylinder being circular, the base having a radius of 10 feet, and the altude being 7 feet, the number of square feet in the base is 100 x 355113, or 314 59, which, multiplied by 7, gives 2202 13, the number of cubic feet in the cylinder. To find the number of square units in the surface, multiply the number of linear units in the circumference of the base by that in the altitude. Thus in the preceding case the number of feet in the circumference of the base is 20 x 355113, or 62 918, which, multiplied by 7, gives 440 426, the number of square feet in the cylindrical part

presence of the superior rudimentary false molar, being thus directly intermediate, in point of dentition, between this genus and the Herpestes; and it is not a little singular that it should bear precisely the same relation to both these genera in the form and number of its toes. The Herpestes have rudimentary false molars both in the upper and under jaws, and five toes both before and behind; the Cynictis has rudimentary false molars only in the upper jaw, five toes on the fore and only four on the hind feet; the Ryzæna has no rudimentary false molars in either jaw, and four

[Skull of Cyuictis ]

b

a, seen from above; b, profile of the same; e, half of erauium seen from below, showing the position of the teeth in the upper jaw d, half of the lower jaw seen from above (from Mr. Ogilby's figure)

toes only, as well on the anterior as on the posterior extremities. These traits of zoological character strongly point out the true natural relations of all these animals, and demonstrate the relative positions which they occupy in the system of nature. With the single exception of the Proteles, there is no other known genus of the Viverra family which possesses the same number of toes and complete digitigrade extremities which form so prominent a character in the Cynictis. Here however all analogy ceases between these two genera. It is true that we are at present ignorant of the adult characters of the dentition of the Proteles; when we become better acquainted with this important part of its organization, we may perhaps discover additional points of relation between it and the present genus; but in all its most striking external characters it is completely different, and seems to occupy an intermediate station between the Dogs, the Civets, and the Hyaenas. In addition to these characters the Cynictis may be readily distinguished by its external form and appearance from all conterminous genera. It has a short head, contracted suddenly in front of the eyes, and forming a small naked muzzle, divided by a longitudinal furrow; the ears are short and elliptical, naked inside, and directed forwards; the body long and slender; the tail bushy, and two-thirds of the length of the body, and the whole external form and appearance not unlike that of a Ferret or Ichneumon. The temporal fosse are separated from the orbits by a complete rim of bone.

Example. Cynictis Steedmannii (Ogilby), named after Mr. Steedman, to whom zoologists are indebted for a knowledge of the animal.

Description.-Length of the head from the muzzle to the root of the ear, 24 inches; length of the ear. of an

NB. Cryptoproctra, Bean, described subsequently in 'Zool. Trans.' has toes and claws on each foot. [VIVERSION]

inch; breadth of the ear, 14 inch; length of the body from the muzzle to the root of the tail, 1 foot 6 inches; length of the tail, 1 foot; height at the shoulder, 7 inches; height at the croup, 7 inches. Hair moderately fine in quality, much resembling that of a dog, smooth and close on the body, long and bushy on the tail. The general colour, as well as the whole external appearance, precisely that of a small Fox, bright red over the entire body, head, and extremities, deep and uniform on the back, but mixed with silvery grey on the cheeks, neck, sides, and tail, arising from a mixture of hairs tipt with grey, and dispersed through the fur of these parts. The breast, belly, and legs, unmixed red; and the tail, which precisely resembles the brush of a fox, covered with long bushy hairs of a sandy red colour at the roots, dark brown in the centre and grey at the points the last two inches at the tip of the tail uniform dirty white. Hairs of the body not annulated as in Herpestes and the Suricate, and altogether of a finer and more furry quality. External form and appearance comparable with those of the Ferret and Egyptian Ichneumon, but probably standing higher on the legs as being more completely digitigrade. Locality.-Uytenhage, on the borders of Caffraria.

(Ogilby.)

Mr. Ogilby thus concludes his observations on this interesting animal:-'In consulting the works of travellers through the colony of the Cape of Good Hope, I have been able to find but two notices which seem clearly to refer to this animal; one by Dr. Sparrman, the other by Mr. Barrow. The first of these authors in the English translation of his 'Travels,' vol. ii. p. 184, has the following passage. "Two other small animals, which probably likewise belorg to the Fiverra genus, I had only a hasty glimpse of in this colony. The one we saw and gave chase to between the two Fish Rivers made its escape from us, however, by running into a hole underground, and seemed to be somewhat less than a cat, though longer in proportion. The colour of it was a bright red." It is true that this passage records no observation by which we can with certainty refer the animal to which it alludes to, the Cynictis Steedman, but the size, colour, and habitat are so perfectly similar in both cases, as to render their identity extremely probable. In the following extract however from Barrow's Travels, vol. i. p. 185, the characters are fully reported "Upon these parched plains" (those of Camdebo, on the eastern confines of the colony) "are also found several species of a small quadruped which burrows in the ground, and which is known to the colonists under the general name of Meerkat. They are mostly of the genus of animals to which zoologists have given the name of liverra. An eagle making a stoop at one of these, close to where we were passing, missed his prey, and both fell a sacrifice, one to the gun, the other to the dogs. Both the bird and quadruped appeared to be undescribed species.... The Vicerra was wholly of a bright chestnut colour; the tail shaded with black hairs, bushy, straight, and white at the extremity; ears, short and round; on the fore-feet, five, and on the hind, four toes; the body and tail each one foot long." There can be no doubt,' continues Mr. Oguby, of the animal to which this description refers, a description more minute and accurate than we generally find in the works of travellers. It agrees in every point with the species which forms the subject of the present memor