SUB-CLASS II 



hllSKANCHIATA 



001 



with the ventral side coin avi-, tin- coils not in contact, composed of nacreous substance ; 

 septa concave; protoconch globular. Sipliunrlr ventral and iiiarLfin.il in po.-itinn, 

 completed by siphonal funnels extending Ixitween the septa. Prosiphon present. 

 Recent ; inhabits tropical seas. [For description of the animal see " Zoology," Part 

 1 A XXIII., of Challenger Reports, 1895.] 



Sub-Order B. SEPIOIDEA. Cuttle-fishes. 



Shell internal, without differentiated phragmocone and guard, but consisting essenti- 

 ally of proost racum or "pen," which is either oval, or narrow and elongated. Arms ten 

 in n umber, provided with suckers or hooks. Ink-bag present. 



Family 1. Sepiophoridae. Fischer. 



Skeleton calcareous, elongated-oval, terminating posteriorly in a thickened mucro 

 which represents a rudimentary phragmocone and rostrum, and encloses a conical cavity. 

 Siphuncle wanting. 



The thickened posterior mucro is a rudimentary structure probably corresponding 

 to the guard of Belemnoids, and 

 its conical cavity to the alveolus 

 Belosepia retains a vestigial 

 chambering but no siphuncle, 

 and in Sepia a recognisable 

 phragmocone is wholly wanting. 



Belosepia, Voltz (Fig. 1254). 

 As a rule only the posterior 

 portion of the proostracum is 

 preserved. This ends in a bent 

 spine, which is thickened an- 

 teriorly, laterally expanded, and 

 contains near the apex a conical 

 alveolus. The latter showa on 

 the dorsal side incomplete traces 

 of septa, and a wide funnel-like 

 depression occupies the place of a 

 siphuncle. Eocene ; not uncom- 

 mon in Paris Basin. 



Sepia, Lam. (Fig. 1255). 

 Proostracum of equal length 

 with the mantle, elongated-oval, 

 rounded anteriorly, thickened 

 posteriorly and terminating in a 



short mucro. The latter contains 

 a conical alveolus. External walls 



Fio. 1254. 



Belosepia Blainvillei, Desh. 

 Eocene ; Auvers, near Paris, 

 of proostracum consisting of tWO A > Posterior end of shell, 

 , . , , , ventral aspect. ]i, Same from 



brittle calcareous laminae, the side (after Deshayes). 



In- 



Fiu. 1255. 



Septa offlcinalis, Linn. Recent. 

 Ventral view of shell. A, Cal- 

 careous lamellae of proostracum. 

 li, Position of rudimentary ph rag- 

 mocone in front of mucro, 2/3. 



separated by a horny layer, 

 ternally 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 familiar cuttle-bone of commerce or 

 ossa Sepiae, is the pen of Sepia officinalis, Linn., and is found in great quantities 

 along the coast of certain countries. Several Tertiary species known. 



