CIO 



M O L L U S C A. 



Moiiusca. in part imbricated. Each layer is attached to the con- 

 > """"Y~""^ cave surface of the dermal plate by the upper extremi- 

 ty and the two sides, while the inferior or caudal ex- 

 tremity is free. The inferior and first formed layers 

 are short, and occupy the base and middle, and rise 

 from the plate under a more obtuse angle than the 

 new formed layers, which are both the longest and the 

 broadest. 



Each layer, which is about one-fiftieth of an inch in 

 diameter, consists of a very thin plate, whose dermal 

 surface, when viewed with a magnifier, exhibits nume- 

 rous brain-like gyrations. From the ventral surface of 

 this plate arise numerous perpendicular laminas, which, 

 when viewed laterally, appear like fine parallel threads, 

 but when examined vertically, are found to be waved, 

 and fold upon themselves. -Next the plate they are 

 thin, and not much folded ; but towards their other 

 extremity, they become thicker, striated across, and 

 more folded, with irregular margins. On the thick 

 tortuous even ends of these lamina, the succeeding 

 plate rests, and derives from them the peculiar mark- 

 ings of its surface. These laminae are closely set, ir- 

 regularly interrupted, and occasionally anastomose. 

 M. Cuvier (Mem. sur la Seiche, p. 47.) states, erro- 

 neously, that these laminae are hollow pillars disposed 

 in a quincunx order. 



The term bone has been improperly applied to this 

 complicated plate ; " for," (according to Mr. Hatchett, 

 Phil Trans, Vol. Ixxxix. p. 321.) " this substance, 

 in composition, is exactly similar to shell, and consists 

 of various membranes hardened by carbonate of lime, 

 without the smallest mixture of phospate." 



This bone was formerly much prized in medicine as 

 an absorbent, but is now chiefly sought after for the 

 purpose of polishing the softer metals. 



The most remarkable species of this genus is the 

 Sepia officinal, which is distinguished from the others 

 by its smooth skin. It inhabits the British Seas, and 

 although seldom taken, its bone is cast ashore on dif- 

 ferent parts of the coast, from the south of England to 

 the Zetland isles. 



5. Loligo, or Calamary. This genus, the larger 

 species of which are known to the fishermen under the 

 denominations Sleeve-fish, Hose- fish, and Anchor- fish, 

 is distinguished from the former by having the sides of 

 the sac furnished only partially with fins. The dorsal 

 plate is flexible and corneous, imbedded in the sub- 

 stance of the sac, and is multiplied with years. The 

 suckers are disposed on the arms and feet in a double 

 row. 



The species of this genus have not been investigated 

 with much care. Four sorts have been found in our 

 seas, which are probably the types of as many differ- 

 ent genera. In two of these the sac is cylindrical 

 above, and compressed towards the tail, with which the 

 fins on each side are united. 



In the Lolign vu/garis, the fins, together with the 

 tail, form a rhomboidal expansion. The feet are near, 

 ly of the same length with the body, and covered with 

 suckers only near their distal extremity. There is no 

 eye-lid. The bone is elliptical, elongated, and pro- 

 duced at the upper extremity, with a groove along the 

 middle. The appendage to the stomach is straight, 

 and the oviduct is single. 



This species is described and figured by Borlace, in 

 his Natural History of Cornwall, p. 260. Tab. xxv. 

 f. '27; and by Pennant in the British Zoolo%y, Vol. iv. 

 p. 53. No. 43. Tab. xxvii. 



In the Loligo sngittata, the fins, with the tail, form a 

 triangular expansion ; the feet are shorter than the bo. 



dy, and .covered with suckers nearly to their base. Molluie. 

 There is a duplicature of the skin round the eye, form- "v"' 

 ing an eyelid. The bone is narrow, thin, expanded at 

 both ends, and strengthened by two marginal ribs, and 

 one in the centre. The appendage to th stomach is 

 spiral, and the oviduct double. 



This species has hitherto, in this country, been con- 

 founded with the preceding. It is, however, the one al- 

 luded to by Monro, secundus, in his Structure and Phy- 

 siology nf Fiihes, p. 62, tab. xli, xlii. His specimens 

 were probably obtained from the Firth of Forth. The 

 same species has occurred to the writer of this article in 

 the Firth of Tay. 



In the two remaining species the fins which occur 

 near the tail are not continued to its extremity. The 

 Loligo media has the sac long, slender, and rounded. 

 The fins on each side are of an elliptical form, and the 

 tail is produced beneath into a point. This appears to 

 be a rare species. It is figured by Pennant in his 

 British Zoology, vol. 4. tab. xxix. No. 45. 



In the Loligo sepiola, the body is nearly of equal di- 

 mensions in length and breadth; the fins are thin and 

 rounded, and the outline of the tail serrficircular. 

 It is figured by Pennant in the British Zoology, 

 vol. 4. tab. xxix. No. 46. This species appears to 

 be rare. It is recorded by Pennant as having been 

 taken off Flintshire. A specimen now before us was 

 obtained in the Firth of Forth at Kirkaldy, by Mr. 

 Chalmers, surgeon of that town. 



Various species of the Sepiacea were formerly used 

 as food ; and Aristotle informs us that they were con- 

 sidered in the best condition for the table when nearly 

 ready for spawning. The modern Italians and Greeks 

 are said to use them still as an article of diet, and to 

 consider the eggs as a great delicacy. In our own 

 country, Moutfet considered them excellent meat, when 

 boiled with wine and spices. 



The animals of the second great division of the cepha- 

 lopoda may be considered as nearly unknown. The 

 shells were united by Linnaeus in one genus, which he 

 termed Nautilus ; but, in consequence of their peculiar 

 characters, they have been sub-divided into many new 

 genera. The animals belonging to two of these modern 

 genera, spirula and nautilus, which both belong to the 

 spiral multilocular tribe, have been imperfectly de- 

 scribed. 



The shell of the Spirula has the whorls separate, the 

 mouth orbicular, the chambers perforated by a tube, and 

 the last cell produced into a tube. The animal resem- 

 bles the Sepia, and the shell is concealed under the skin, 

 and occupies a similar situation to the cuttle-bone. 



The animal of the Spirula vulgaris appears to be very 

 common in the West Indies, as the chambered spiral 

 extremity of the shell is frequently brought to this 

 country. 



In the shell of the restricted genus Nautilus, the turns 

 of the spire are contiguous, the last whorl embraces the 

 others on the sides, and the chambers are perforated by 

 a tube. The animal of the Nautilus pompilius, accord- 

 ing to Rumphius, lodges in the last chambers, and is 

 fixed by a ligament which descends into the tube. 

 The arms which surround the mouth are destitute of 

 suckers. 



Among the minute shells which occur in the roots of 

 sea-weeds, on old shells, corals, and sertularia?, are 

 many genera of multilocular testacea, some of which have 

 been described in the article CONCHOLOOY. Guided by 

 analogy, naturalists have been disposed to consider these 

 as the productions of cephalopodous mollusca. Their 

 inhabitants; however, have not been examined, and the 



