J. E. GRAY. 585 



to the anterior horny sheath of the Belemnites* 

 Ex. Sepia. 

 Fam. 4. Teuthid^e. Animal, body sometimes oblong 

 and depressed, generally elongated and cylindrical ; 

 with a pair of fins varying in their relative size and 

 position, but generally broad, shorter than the body, 

 and terminal. Shell internal, rudimental, in the 

 form of a thin straight elongated horny lamina, 

 encysted in the substance of the dorsal aspect of 

 the mantle. Ex. * Sepioteuthis, Loligo, Onycho- 

 teuthis, Rossia, Sepiola. ** Loligopsis, Cranchia. 



Tribe Octopoda. 



Fain. 5. Testacea. This family embraces the genus 

 Argonauta, and, perhaps, the fossil Bellerophon. It 

 is denned: Body oblong, rounded; mantle adhering 

 posteriorly to the head ; first or dorsal pairs of arms, 

 dilated and membranous at the extremity : Funnel 

 without a valve, but articulated at its base by two 

 ball and socket joints to the inner sides of the mantle. 

 Branchial hearts with fleshy appendages : No in- 

 ternal horny or testaceous rudiments ; but an ex- 

 ternal monothalamous symmetrical shell, containing, 

 but not attached to, the body of the animal ; which 

 also deposits its eggs in the cavity of the shell. 



Fam. 6. Nuda. Body generally rounded, mantle 

 broadly continuous with the back of the head. 

 Arms connected at the base by a broad web : first 

 pair elongated, and gradually narrowing to a point. 

 Funnel without an internal valve, or external joints ; 

 branchial hearts without fleshy appendages ; biliary 

 ducts without follicular appendages. Shell repre- 

 sented by two short rudimental styles encysted in 

 the dorsolateral parts of the mantle. Ex. Octopus, 

 Eledone. 



2. Pteropoda. 



Mr. J. E. Gray has proposed to divide this small and 

 curious class* into two orders : The first is called Thecoso- 

 mata, because the body is enclosed in a thin shell. The 

 head of the animals is indistinct, the mouth being placed in 

 the centre of the two large wings, which are united into a 



* M. Emile Blancliard's anatomy of the ganglia of the Ptcropods con- 

 firms the view of Cuvier in making a separate clas* of them, in opposition 

 to Blainville, who would mingle them with the (iastcropods. — Syst. Ncrv. 

 chez les Invertebres, 10. 



