128 MR. OWEN'S DESCRIPTIONS OF 



nitid(B, including the genera Belemnites, Actinocainax, Pseudohelus, he, offer the trans- 

 ition from the SpirulidfE to the Cephalopods in which the internal shell is still calca- 

 reous, but in which the traces of the camerated structure become very obscure. Such 

 is the condition of the shell in the SepiadcB, or third family, represented by the common 

 Cuttle-fish {Sepia officinalis, Linn.). Besides the character derivable from the modifi- 

 cations of the shell, the species hitherto observed of this family present lateral fins, ex- 

 tending the whole length of the mantle ; and the marginal horny lining of the suckers 

 is entire, or only minutely denticulated ; but this latter is a character rather of generic 

 than of family importance. 



The fourth family of Decapodous Dibranchiata, I propose to term Teuthidee, from the 

 name reuSoc, applied by Aristotle to the Calamaries or typical genus of the family. The 

 principal character of this family reposes on the horny condition of the shell, the rudi- 

 ment of which exists as a single lamina, more or less developed, and encysted in the 

 substance of the dorsal aspect of the mantle : the form of the body in this family is 

 mostly elongated and cylindrical, and the pallial fins are generally broad, shorter than 

 the body, and terminal. The genera included in this family may be arranged in two 

 groups, according to the structure of the funnel. In section A, or those in which the 

 funnel is articulated at its base to two internal ventro-lateral cartilaginous prominences 

 of the mantle, may be ranked the genera Sepioteuthis, Bl. ; Loligo, Cuv. ; Onychoteuthis, 

 Lichtenstein ; Rossia, Owen ; Sepiola, Leach. In all these genera, moreover, the funnel 

 is provided with an internal valve. In section B, or those in which the funnel is ad- 

 herent at the ventro-lateral parts of its base to the mantle, may be ranked the genera 

 Cranchia, Leach, and Loligopsis, Lam. The latter genus, besides the common absence 

 or loss of its superadded tentacles, manifests an affinity with the Octopodous Dibran- 

 chiates, in the absence of the valve of the funnel ; and in both genera the transition to 

 the same group is indicated by the absence of the fleshy appendages to the branchial 

 hearts. 



The uninterrupted continuation of the mantle with the posterior part of the head or 

 neck, and the confluence of the pallial fins at their posterior extremities, which Dr. Leach 

 uses as family characters, are indicative of generic distinctions only : the proportional 

 length of the arms is even of still less importance. 



The tribe Octopoda, besides the absence of the long peduncles, is characterised by 

 the absence of the pallial fins, and infundibular valve. I subdivide this tribe into the 

 families Testacea and Nuda. Of these the first is represented by the genus Argonauta, 

 and its affinity to the Decapodous group is manifested by the presence of appendages to 

 the branchial hearts, and by the ball and socket articulations of the funnel. The first 

 or dorsal pair of arms support membranous expansions for secreting, repairing, and re- 

 taining the shell. 



The naked Octopods have all or part of the arms connected at their bases by a broad 

 web ; the first pair being elongated, and gradually diminishing to a point. The funnel 



