686 



MOLLUSCA— CEPHALOPODA 



PHYLUM VI 



inlialjits tropical seas. For description of the animal see Keport on Spirula, by 

 Huxley and Pelseneer, in Appendix to Challenger Keports, Zoology, part Ixxxiii., 

 1895. 



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



Shell internal, without differentiated •phragmacone and guard, hut consisting essenti- 

 ally of the proostracum or ^'' pen" which is either oval or narrow and elongated. Arms 

 ten in number, provided with suckers or hooks. Ink-bag present. 



Family 1. Sepiophoridae Fischer. 



Shell or " sepion " a calcareous, elongated-oval plate, terminating piosteriorhj in a 

 thickened mucro which represents a rudimentary guard, and encloses a conical cavity. 

 Siphuncle wanting. 



The thickened posterior mucro is a nidimentary structure 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 from 

 Belemnoids like Beloptera. 



Belosepia Voltz (Fig. 1331). 

 As a rule only the posterior portion 

 of the ijroostracum is preserved. 

 This ends in a bent spine, which 

 is thickened anteriorly, laterally 

 expanded, and contains near the 

 apex 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 uncommon 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 jien 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 I'ods, thus producing a spongy texture. The familiar cuttle-bone of 

 commerce, or ossa Sepiae, is the pen of Sepia officinalis 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. 



Pig. 1331. 



Belosepia hlainvillei De.sli. 

 Eocene ; Aiivers, near Paris. 

 A, Posterior end of shell, 

 ventral aspect. B, Same fioni 

 the sid(! (after Deshayes). 



Fifi. 1332. 



Scpki officltinlis Linn. Recent. 

 Ventral view of .shell, a, Cal- 

 careous shelly plates represent- 

 ing vestigial septation. h, Pcsi- 

 tion of rudimentary phragma- 

 cone in front of mucro, '•^/.■j 



