tumn, and the flesh is said to be preferable to that of any of our other species.

The cat squirrel does not appear to be migratory in its habits. The same pair, if undisturbed, may be found taking up their residence in a particular vicinity for a number of years in succession; and the sexes seem mated for life.

(To be continued).

ART. III. Notice of a species of Rotalia found attached to specimens of Vermetus Bognoriensis. By NATHANIEL WETHERELL, Esq., M.R.C.S., F.G.S., &c.

WHEN I first observed some specimens of Rotalia upon the whorls of the Vermetus Bognoriensis, I imagined that these minute fossil bodies had been casually lodged in some of the small furrows upon its external surface; further observations and additional specimens, however, convinced me to the contrary, and I perceived, on a careful microscopic examination, that not only were the Rotalia attached to the Vermetus, but that in several instances they were absolutely imbedded in the substance of the shell itself.

27

a

On my first discovery of these remains, I briefly alluded to the circumstance in a paper read before the Camden Literary and Scientific Institution, (April 26th, 1836), subsequently published in the 'London and Edinburgh Philosophical Magazine.' I have since considered that it would be an interesting record to have them engraved, exhibiting the fossils of the natural size, together with magnified figures, as annexed.

1

"Observations on some of the Fossils of the London Clay, and in particular those Organic Remains which have been recently discovered in the Tunnel of the London and Birmingham Rail-road. By Nath. Thos. Wetherell, Esq., F.G.S., M.R.C.S., &c." The London and Edinburgh Philosophical Magazine and Journal of Science, Vol. ix., Dec. 1836, No. 56.

Fig. 27, a, which is exceedingly minute, is accompanied with three magnified views; and fig. 27, b, with the same.

I was induced to have both specimens represented, as there are some slight differences between them, which, unless depending upon particular periods of growth, may be considered sufficient to constitute them different species or varieties.

The locality whence I obtained my specimens is the tunnel of the London and Birmingham rail-road, near Chalk farm. Although I have examined several hundreds from this place, I have only found about eight or nine with the Rotalia attached. I have had in my possession at different times some thousand specimens of Vermetus Bognoriensis, from Highgate, Bognor, and Sheppey, but I have never before noticed any minute shell or coral attached to them.

It was at first my intention to have given a specific name; the present fossil however appears so closely to resemble a species found at Grignon, that I have thought it better not to do so.

Highgate, March 12th, 1839.

ART. IV.-Description of a new fossil Avicula, from the Lias Shale of Somersetshire. By SAMUEL STUTCHBURY, Esq., Curator to the Bristol Philosophical Institution, &c.

28

AVICULA longicostata.

Shell inequilateral, with six raised coste radiating from the umbo, each rib extending far beyond the margin of the valve; minutely striated between the ribs.

This very elegant fossil is remarkable from the great extension of the ribs which radiate from the umbo, in several instances extending more than an inch beyond the margin of the valve. In the five specimens which have come under my observation, there appears to have been a determinate stoppage of growth, which is evidenced by a raised line crossing the disc of the shell and spinous terminations of the firstformed ribs.

The internal characters determine the genus to which it belongs, while the external characters alone would have left me in doubt to which of the following genera it most probably belonged; viz. Aricula, Pecten, or Plagiostoma. The number of ribs (six) appears to be a constant character, at least judging from the specimens which have already come to hand.

For this beautiful fossil we are indebted to the excavations made through the lias shales along the line of the great western railway, at Saltford, between Bristol and Bath. Avicula Cygnipes, figured in Phillips's 'Geology of Yorkshire' resembles it, but the two are sufficiently distinct to justify their separation.

Bristol, January 16th, 1839.

ART. V.-On the Anatomy of the Lamellibranchiate Conchiferous Animals. By ROBERT GARNER, Esq., F.L.S.,

(Continued from Page 129).

DIGESTIVE SYSTEM.

All these animals derive their nourishment from the animalcules and other nutrient particles drawn in with the water, by means of the currents excited by the ciliated branchia and tentacles. The particles are collected at the anterior part of the cavity of the mantle, and are conveyed into the œsophagus by means of tentacles and lips, strongly ciliated internally for that purpose. In some species, as the Pecten, the foot seems a prehensile organ of the food, and the curious foot of the Spondylus is perhaps of some use in this way. The tentacles are precisely similar to the branchia in structure, being commonly membranous, striated by the vessels, and ciliated; and their vascular system is often continuous with that of the branchia, so that they probably serve the purpose of respiration also. They are generally triangular in shape. In the Nucula, the external one is large and spiral; in the Corbula

they are long and volute. They are large in the Tellina and similar genera; small in Modiola, Mya, Psammobia, &c. When lips are developed the tentacles are small. These are of a fringed appearance in Pecten, Spondylus, &c., more foliated in Chama. The mouth is small in Venus, &c., larger in several of the Monomyaria. The œsophagus, generally very short, is however occasionally pretty long, as in the Pholas. Home describes salivary glands in the Teredo, but these I have not been able to find; and Poli, bodies which he supposes to be such in the Pinna. The stomach is always in the centre of the liver, and the bile ducts enter it by one or more orifices. Into the stomach projects the extremity of a lengthened cartilage, the "crystalline style" of Poli. The other extremity has been described as going to the foot, and adding to the elasticity of that organ. This body is of various shapes, and has at its superior extremity a cartilaginous membrane, the "tricuspid body" of Poli. This lies at the inferior surface of the stomach, and its extremities enter the bile ducts. The crystalline style is wanting when the foot is small; the membrane is always present. The former is evidently analogous to the tongue of the Patella and other cephalous Mollusca; it is secreted from behind and comes forward into the stomach; the membrane at its extremity is analogous to the membrane always found in a similar situation at the end of the tongue in other Mollusca. The apparatus of mastication in the Gasteropoda is then in the Lamellibranchiata partly subservient to digestion, but has also another use assigned to it-the giving elasticity to the foot, or, in the Anomia, where its extremity is seen in the mantle, the preserving in its situation the free extremity of the left lobe of the latter part.

These organs have been supposed by Poli to regulate the flow of bile; which appears probable. By Carus they are imagined to be concerned in the function of generation, which supposition is not warranted by the facts; but, on the contrary, there are grounds on which we may infer that it is unlikely. The duodenum or first part of the intestine is wider than the remainder and is by some called a second stomach. It sometimes originates from the true stomach distinct from the style, as in Mactra, Pholas, 3 some species of Solen, &c. Sometimes the style lies in a groove of the duodenum, which

1 Poli.

2 Lehrbuch, v. 2.

3 The digestive system of the Teredo only differs from that of the Pholas in its greater length.

leaves its extremity, as in some Tellinæ, &c., or diverges from its side at a greater or less distance from the end, as in Cardium, Solen vagina, &c. The parietes of the duodenum are glandular. The remainder of the canal has many veins originating from it, which perhaps act the part also of lacteals. The extremity of the duodenum is always near the pedal pore and perhaps the ritellus of the embryo so enters. The intestine varies much in length. As shewn by Poli, those species which are fixed have it shortest. In Anomia it is not an inch long, and makes no turn; it has a rounded projecting process in its whole length. A similar projection is seen in other genera. The convolutions of the intestine interwoven with the liver and ovaries, are generally contained in great part in the foot. In the Monomyaria, in the Mytilus, Pinna, &c., it makes only two or three turns, the last often surrounding the stomach. In the fresh water species it is longer by a turn or two; longer still in Pholas, Mya, Venerupis, Tellina, &c.; but longest of all in Cardium, Donax, Venus, Mactra, and some other genera, where it is sometimes ten or twelve times the length of the animal. The intestine, having made its convolutions, is directed towards the heart, through the ventricle of which it commonly passes, and ends on the posterior muscle by an opening, which, in some species, has a divided margin. This anus is situated between the lobes of the mantle, and opens into the superior of the two tubes, when they exist. In the oyster the ventricle is not perforated by the intestine, the heart being in a different situation. In the Anomia the heart lies upon it. When there are two ventricles, as in Arca, Lima, and certain Pectunculi, the intestine passes between them. In the Unio it has been described that the intestine makes its escape from the cavity of the heart to re-enter it again; such a description is not taken from the normal disposition of the animal. The curious circumstance of the perforation of the ventricle by the intestinal tube appears to be a result merely of the disposition of the parts.

The liver, in all the Lamellibranchiata, surrounds the cavity of the stomach, into which its secretion of greenish bile is poured by one or more ducts. It has no vena porta going to it, but its arteries, and hepatic veins are large. Its situation is at the anterior and superior part of the animal, and it is composed of a multitude of oval granules, differing in size in different species, opening into the termination of the ramuscules of the duct.