in review the opinions and statements of these authors, as well as of Blainville, Laurillard, Gervais, Pomel, Lartet, and Sismonda, on these species, and on the specimens which these observers had severally described, sometimes under additional specific names. He then described the characteristic peculiarities both of the molars and of the symphysis of the lower jaws in these three species; and showed that the molars from the Crag Mastodon were, like those of Tetral. arvernensis, characterized by four-ridged molars, with their conical points more or less alternating, and with their valleys blocked up; and that they essentially differed from the molars of the Triloph. angustidens from Simorre, Dax, &c., and from the Tetral. longirostris of Eppelsheim. The M. arvernensis of Montpellier, Auvergne, Italy, &c. had no lower tusks; and the author is of opinion that the only specimen which has been figured and described as one of the lower tusks of the Crag Mastodon is a terminal fragment of one of the upper tusks of that species. From osteological considerations it appears that Tetral. arvernensis was of a low and heavy make; that Tetral. longirostris was of similar general proportions; and that Triloph. angustidens was higher in its limbs and of a comparatively light and slender shape. In his observations on the geological age and associated faunas of the formations in which these species severally occur, Dr. Falconer observed that Trilophodon angustidens is a characteristic species of the miocene falunian beds throughout Europe, and is associated with Triloph. tapiroides in the Faluns of France and the upper freshwater Molasse of Switzerland. Tetralophodon longirostris is an important member of the Eppelsheim fauna, which, though its determination is accompanied with great difficulty, appears to be identical in its leading features with that of the falunian deposits of France and Switzerland. The Tetralophodon arvernensis is characteristic of the pliocene fauna; and it had a very extended range of habitat over Europe, accompanying Loxodon meridionalis (Nesti) in Tuscany,Trilophodon Borsoni, Loxodon priscus, and Euelephas antiquus in Piedmont and Lombardy,-Loxodon meridionalis at Montpellier,-and Tril. Borsoni, Lox. meridionalis, and Lox. priscus, in Velay and Auvergne. After having reviewed the circumstances under which Mastodon remains occur in the British strata, Dr. Falconer concludes that,-1st. The Mastodon remains which have been met with in the Fluvio-marine and Red Crags belong to a pliocene form, namely Tetralophodon arvernensis. 2ndly. The Mammalian fauna of the Red and Fluvio-marine Crags, regarded as a whole, bears all the characters of a Pliocene age, and is identical with the Subapennine Pliocene fauna of Italy. 3rdly. The Red and Fluvio-marine Crags, tested by their mammalian fauna, must be considered as beds of the same geological age. Throughout this paper, for the sake of clearness, the subgeneric names have been used in designating the species. The author, finding that the name Elasmodon, applied to the third group of Elephants, in the 'Fauna Antiqua Sivalensis,' in 1847, had been previously used for a fossil fish, has abandoned it, and applies the term Euelephas in lieu of it. April 22, 1857.-Colonel Portlock, R.E., President, in the Chair. 1. "Description of a Crustacean from the Lias Bone-bed." By Mr. 2. "Description of a Crustacean (Pygocephalus Cooperi) from the Coal-measures." By Prof. Huxley, F.G.S. This new and remarkable Crustacean is represented by three specimens in ironstone nodules; each presenting, from the breakage of the nodules, the ventral surface in relief, with the corresponding impression. Two of the specimens are the property of R. S. Cooper, Esq., of Bilston, and were obtained from the shale overlying the upper or thick coal-beds of that place, and were associated with fragments of Pecopteris. The other specimen belongs to the Manchester Museum, and was derived from the coal-shales at Medlock Park Bridge. The animal is about 1 inch in length; its ventral surface presents at one extremity a quadrate disk, about inch long, furnished anteriorly with two pairs of jointed appendages (the large outer pair being antennæ; the inner smaller pair, the antennules), and margined by the narrow flattened edges of the carapace. The central portion of the body is about an inch in length, and is divided into a series of seven thoracic segments, composed of one medial and two lateral subquadrate plates, and increasing in size backwards by the gradual widening of the medial plates. Each segment is provided with a slender jointed limb on either side: the limbs are directed either forward or outward; and in one instance at least there is clear evidence of a fine, jointed filament, or exopodite, attached to limb (the fifth). The posterior extremity of the specimen (constituted by the termination of the large abdomen, bent upon itself) is much wider than the other, and has the form of a semicircular disk; the base of the semicircle forming the widest part of the body, and being about half an inch distant from the centre of the curve. This semicircular, caudal plate is traversed by a linear depression at about the middle of its length; another transverse depression mark is near its periphery; and, on clearing away the matrix from the opposite surface of one of the specimens, this portion was found to be continued underneath with a greater convexity, and with indications of other transverse lines of depression, bounding dorsal segments. The surface of the caudal plate is also divided longitudinally by two depressions into three broad subtriangular lobes. Prof. Huxley described in detail the process of his determination of the above-described characters from the successive examination of the several specimens; and intimated that at first, so problematical were the characters afforded by one or two specimens only, that the broader extremity was regarded as possibly the cephalic buckler of an anomalous Apus-like crustacean, with its dorsal surface presented to view. Subsequent examination of the specimens kindly lent by Mr. Cooper enabled the author to take a different and more probable view of the structural relations of these interesting fossils. Mr. Huxley pointed out that the Pygocephalus Cooperi has some peculiar relations with the little Mysis or Opossum-shrimp, especially in the schizopodous character of its thoracic appendages, in the proportional size of the carapace, and in the gradual increase in width, from before backwards, of the sterna of the thoracic somites. In the proportions of its abdomen, however, the Pygocephalus approximates more nearly to the true Stomapoda; and a Goñodactylus bent upon itself presents an appearance in some respects very analogous to that of the fossils in question, 3." On the Geology of Strath, Isle of Skye." By A. Geikie, Esq. Communicated by Prof. Ramsay, F.G.S. In his introduction the author referred to Prof. Jameson's mine. ralogical observations on this district, to Dr. Macculloch's subsequent and more extensive descriptions, and to Sir R. Murchison's further account of the stratified rocks of the eastern coast of Skye. The character and sequence of the liassic beds of Strath were then detailed; the author pointing out some instances in which his recent observations do not bear out Dr. Macculloch's account of the geology of this part of Skye. Mr. Geikie enumerates the following liassic beds, as occurring in Strath:-1. (lowest, and resting on the red sandstone and quartzite of Sleat) a fine conglomerate, 2 to 3 feet thick, seen at Heast; 2. green and yellow sandstone, 3 to 15 feet; 3, limestone, 1 foot: coral-bed (with Isastræa), 2 feet; 4. calcareous grit, 7 to 8 feet; 5. limestone with occasional seams of shale: Nos, 4 and 5 contain Ammonites, Gryphaa, and Pentacrinites: Nos. 2 to 5 are seen at Lussay; 6. white sandstone; 7. dark brownish-grey sandy shale ; 8. calcareous brecciated conglomerate, seen at Obe Breakish ; 9. limestones and shales in alternate bands (Broadford); 10. calcareous grits with Gryphaa, seen at Corry: Nos. 1 to 10 are referred to the Lower Lias; 11, dark grey or brown sandy micaceous shales (Pabba), with numerous fossils; and 12. dark calcareous shales (Scalpa), with Pecten, Ostræa, &c.: Nos. 11 and 12 are referred to the Middle Lias. The dip of these beds along the author's section from their base at Lussay to their top at Scalpa House is N.W, at an angle of 5° to 8°; and he estimates their thickness at about 1500 feet. Taken as a whole, the liassic beds of Strath appear to form a great synclinal trough, striking N.W. to S.E., bounded by syenite and red sandstone, and ridged up along its centre by an anticlinal axis. Mr. Geikie, in describing the several exposures of the beds along the north and south coasts of Strath and in the interior, particularly noticed the occurrence of white quartzite in the lower limestone near Suisnish, and the limestone-breccia skirting the long sandstone-ridge traversing Strath. The igneous rocks, comprising, 1st, the great eruptive syenitic masses, and 2ndly, the innumerable dykes of augitic trap, were then described; the junctions of the syenite with marble and with shale, and the metamorphism of the calcareous rocks, being specially illustrated. The igneous eruptions in Strath appear to have been all posterior to the middle lias; the first period of volcanic activity gave rise to a profusion of trap-dykes traversing every part of the district, but not materially altering the position or texture of the strata; subsequently vast tracts of syenite tilted up the lias-beds, and extensively metamorphosed them; lastly, great masses of fine-grained syenite, associated with greenstone-dykes, were intruded among the beds without either tilting or altering them to any great extent. This paper was accompanied by a note on Mr. Geikie's fossils by Dr. Wright. Isastræa Murchisoni (sp nov.), Ostræa arietis, and Car. dinia concinna were found at Lussay: Belemnites elongatus, B. paxillosus, B. breviformis, Ammonites Jamesoni, A. brevispina, A. Davæi, Trochus imbricatus, Pholadomya ambigua, Pleuromya Scottica (sp. nov.), P. unioides, Unicardium cardioides, Pinna folium, Mytilus scalprum, Lima gigantea, L. Hermanni, Limea acuticosta, İnoceramus ventricosus, Pecten æquivalvis, Plicatula spinosa, Gervillia Maccullochii (sp. nov.), Gryphæa cymbium, G. obliquata, and Rhynchonella tetrahedra occur in the Pabba shales. Pecten æquivalvis and Avicula, sp., are described as occurring at Scalpa. YOUR LXII. Intelligence and Miscellaneous Articles. ON THE TEMPERATURE OF FOAM, To Dr. Tyndall, F.R.S. &c. Museum of Practical Geology, DEAR SIR, YOUR remarks in the last Number of the Philosophical Magazine, on the Temperature of Foam, recall to my mind an observation of a similar kind made by myself and my friend, Mr. James Simpson, jun., when on a pedestrian excursion in Surrey in December 1855. Our attention was arrested, on arriving at the last lock on the river Wey, at the distance of about half a mile from the point where it empties itself into the Thames, by the production of an extraordinary amount of foam, in consequence of the falling of the river over a weir. This foam was not only unusual in amount, but had a peculiar soapy appearance, and on dipping the hand into it was found to be quite warm fortunately we had a thermometer with us, and were therefore enabled to measure the extent to which the temperature of the foam exceeded that of the water on which it was formed. The temperature of the water was 42°.5 F., whilst that of the foam was 45°, so that the foam was 2°.5 warmer than the water. The thought immediately struck me that its warmth must be due to the air enclosed within it; and if such were the case, it should have a temperature intermediate between that of the water and the air. And such really was the case; for the air, though feeling very cold in consequence of a strong easterly wind blowing, did not fall below 50° F. I may state that the phænomenon appearing to me very curious at the time, considerable care was devoted to the observation of these temperatures, the thermometer being allowed to remain long enough in each medium to become quite stationary. I am, Sir, Yours respectfully, HENRY M. WITT, F.C.S., Assistant Chemist to the Government School of Mines. [I have a strong impression that the temperature of the foam in my case was much higher than that of the air. I, however, judge from my feelings merely, and I know that these are liable to error. A small india-rubber balloon, for example, held in the hand feels warm.-J. T.] DESCRIPTION OF A NEW BAROMETER. BY M. DAVOUST. This barometer is founded on the following principle. Suppose a cylindrical glass tube, in a vertical position, containing a small column of mercury, and of which the extremities may be opened and hermetically closed at pleasure. Let S be the upper and I the lower extremity; the column of mercury is in contact with S, which is closed. I is at first open, then reclosed; S is opened: the mercury sinks in small quantity. When it has again acquired its position of equilibrium, S is again closed and I opened: a fresh sinking of the mercury takes place. I give the name of operation to the successive opening of the upper and lower extremities. The fall of the mercury at the end of the first operation, is a function of the atmospheric pressure; but this fall is too small to enable us to judge with sufficient exactitude of the pressure of the external air. To remedy this inconvenience, the same operation is repeated until the mercury arrives as close as possible to the extremity I; the total fall of the mercury may then be measured with sufficient exactitude to enable us to judge from these variations, as well as from the number of operations performed, of the variations of the atmospheric pressure. Such is the fundamental idea of the barometer which I call the repeating barometer. It consists essentially of a graduated glass tube, furnished at its two extremities with valves kept closed by a spring, and which may be opened by means of a kneed lever. But to make use of the instrument there are some essential conditions to be fulfilled, and this is the purpose of the construction which I describe in detail in my memoir. Thus the caoutchouc forming the valves does not bear immediately upon the large glass tube, for some drops of mercury might remain adherent to it, which would render the observations |