MOLLUSC A. 435 



corneous or testaceous ribs or plates. The head is divided 

 from the sac on all sides by a neck. The margin of the 

 anus is surrounded with tentacula. 



1. Sepia. The sac is furnished on each side through- 

 out its whole length with a narrow fin. 



The suckers are irregularly scattered on the arms and 

 feet. The back is strengthened by a complicated calca^ 

 reous plate, lodged in a peculiar cavity. This plate has 

 been long known in the shop of the apothecary under the 

 name Cuttle-fish bone, which was formerly much prized 

 in medicine as an absorbent, but is now chiefly sought 

 after for the purpose of polishing the softer metals. It 

 is somewhat ovate, flatly convex on both sides, and thick- 

 est where broadest. The superior half, or the one next 

 the head, is the longest, rounded at the extremity, and 

 thin. The inferior portion becomes suddenly narrow, 

 and ends in a point. It may be considered as consisting 

 of a dermal plate, concave on the central aspect, having 

 its concavity filled up with layers which are convex on their 

 central aspect. 



The shells of the genus Nummulites are remarkable for their lenticular 

 form. The external surface is smooth, and the cells are concealed ; but inter- 

 nally the transverse cells are disposed in a spiral discoid form. The cells 

 are imperforate ; they are the Camerinae of Bruguiere, — the Helecites of 

 GtJETTARD, — and the Discolithes of Fort is. This last author supposes, that 

 they are formed in the interior of an animal analogous to the Sepia. The 

 same opinion may be entertained of many other genera of multilocu- 

 lar testacea. Faujas St Fond found a recent specimen of a nummulite 

 among the fragments of the Coralhna officinalis, brought from the island 

 of Corsica. 



It is probable that the genus Lagena, formed from the serpulas lagencB of 

 Walker (Testacea minuta Rariora), belongs to the multilocular testacea ; 

 as in some of the species we have observed the appearances of internal di- 

 visions. 



Ee2 



