686 



MOLLUSCA-CEPHALOPODA 



PHYLUM VI 



• loHf- troi.icil scas For description of the animal see Keport on Spirula by 

 t^^^ti^:^r, in Appendfx to Ghallenoer Reports, Zoology, part Ixxxm., 



1895. 



Order 2. SEPIOIDEA. (Sqiüds and Cuttle-fishes). 

 Shell internal, without differentiated phragmacone and guard, hui consisting essenti- 

 allZthTirroostracurn or ^^pen,^' which is either oval or narrow and elongated. Arms 

 tenin numher, provided with sucJcers or hooks. Inh-hag present. 



I 



Family 1. Sepiophoridae Fischer. 



sepion'' a calcareous, elongated-oval plate, terminating posteriorly in a 



and encloses a conical cavity. 



Shell or 

 thickened mucro which represents a rudimentary 



Siphuncle loanting. 



The thickened posterior mucro is a rudimentary stmcture probably corresponding 

 ^ to the guard of Belemnoids, and 



its conical cavity to the alveolus. 

 Belosepia retains a vestigial cham- 

 bering but no siphuncle, and in 

 Sepia a recognisable phragmacone 

 is wholly wanting. These forms 

 are undoubtedly descended froni 

 Belemnoids like Beloptera. 



Belosepia Voltz (Fig. 1331). 

 As a rule only the posterior portion 

 of the proostracum is preserved. 

 This ends in a bent spine, which 

 is thickened anteriorly, laterally 

 expanded, and contains near the 

 apejc a conical alveolus. The 

 latter shows on the dorsal side 

 incomplete traces of septa, and a 

 wide funnel - like depression 

 occupies the place of a siphuncle. 

 Eocene ; not uneommon in Paris 

 Basin and the London Clay. Rare 

 in Claibornian sands of Alabama. 

 Sepia Lam. (Fig. 1332). Shell 

 or "pen" of equal length with 

 the mantle, elongated - oval, 

 rounded anteriorly, thickened 

 posteriorly and terminating in a 

 short mucro. The latter contains 

 a conical alveolus. Dorsal and 

 ventral walls of the pen consisting of two brittle calcareous laminae, separated by a 

 horny layer. Internally with a mass of extremely fine parallel calcareous lamellae, 

 increasing in thickness anteriorly ; the lamellae separated from one another by 

 minute vertical rods, thus producing a spongy texture. The familiär cuttle-bone of 

 commerce, or ossa Sepiae, is the pen of Sepia oßcinalis Linn., and is found in great 

 quantities along the coasts of certain countries. Several Tertiary species known. 



(?) Gampylosepia Picard. Muschelkalk ; Thuringia. Belosepiella De Alessandri. 

 Eocene : Paris Basin. 



Fi(i. 1331. 

 Belosepi/t hlainvillei Desh. 

 Eocene ; Auvers, near Paris. 

 A, Posterior end of Shell, 

 ventral aspect. B, Same from 

 the sich; (after Deshayes). 



Fio. 1332. 



.S'qria officinalis Linn. Recent. 

 Ventral view of shell. a, Cal- 

 careous shelly plates represent- 

 ing vestigial septation. b, Posi- 

 tion of rudimentary phragma- 

 cone in front of mucro, '^1^ 



