LITUIDJE. 113 



Suborder III. Belemnophora, 



Shell calcareous, internal, chambered ; chamber traversed by a 

 siphon. 



Cephal. Polarnaxia Spirularia Rajin. Anal. Nat. 141. 1815. 

 Cephal. Spiriformia and Belemnomorpha Bronn, Gesch. der Nat, iii. 

 536. 



Fam. VIL LITUIDiE. 



Body subcylindrical, oblong, end rounded ; sometimes furnished 

 with a thickened belt, and "with a small semilunate fleshy fin on 

 each side. Mantle free all round, cartilage on the inner side 

 of the ventral surface linear. 



Byes covered with the skin, with a lower eyelid. Buccal mem- 

 brane without cups. 



Arms. Sessile arms triangular, tapering ; cups numerous, equi- 

 distant, very small, slightly pediceled in six longitudinal series. 

 Tentacular arms elongate, peduncled, cylindrical ; club ? 



Siphuncle conical, with an apical valve. 



Shell internal, shelly, spiral, placed symmetrically at the hinder 

 part of the body, the last chamber being in the central line of 

 the back ; chambered, the chambers furnished with a siphon, the 

 last chamber only large enough to contain a very small part of 

 the animal. 



Spirulidas Owen, Trans. Zool. Soc. ii. 1836; UOrh. Moll. Viv. et 



Fos. i. 160. 306. 1845. 

 Lituidae Gray, Free. Zool. Soc. 1847, 206. 

 Spirularia (pars) RaJin. Anal. Nat. 141. 1815. 

 Sepiacea (pars) Desh. Ency. Meth. iii. 

 Sepiadae (pars) Geinitz, Grund der Verst. 261. 1845. 

 Spiriformia Bronn, Gesch. de Nat. iii. 535. 



1. LiTUUS. 



Synopsis of Genera. 

 A. Shell thin, apex not coated. 



