104 CLASSIFICATION. 



Fischer (see ante, p. 55), that many of these genera were really 

 dibranchiate, and should be ranged with Spirula rather than 

 with Nautilus. I shall imitate the reserve of the latter gentle- 

 man, by making no change in the classification of these fossil 

 forms. 



Family I. OCTOPODI1LU. 



Synopsis of Genera. 



a. Arms with two rows of suckers. 



* Body not finned. 



OCTOPUS. Body rounded. Arms long. Suckers sessile. Third right arm 



of male hectocotylized. 

 CISTOPUS. Differs from Octopus in having a small aquiferous system, 



consisting of a bag with a small pore at its lower edge, upon the web 



between each arm. 

 SC^EURGUS. Body oval ; wider than the head ; arms short ; cups with 



narrowed bases. Third left arm hectocotylized. 



PlNNOCTOPUS. 



b. Arms with a single row of suckers. 



* Not finned. 



ELEDONE. Body rounded, without fins. Third right arm hectocotylized. 

 BOLIT^ENA. More gelatinous than Eledone ; suckers smaller, less 

 developed. 



* * Finned. 



CIRROTEUTHIS. Body with two transverse medial fins ; mantle united 

 to the head nearly all round, by a cervical band ; arms united by a 

 web nearly to their tips. 



Family II. TRKMOCTOPID A'l. 



TREMOCTOPUS. Body rounded, head large, band of the neck very small. 

 Funnel short. Two aquiferous pores in the neck. Third right arm hec- 

 tocotylized, fringed on the sides, and developed in a sack-like aper- 

 ture on the side of the head. 



PARASIRA. Body rounded; head small and short; neck-band rather 

 broad. Funnel long. No water pores in the neck, two at the base of 

 the siphon. Third right arm heetoeotyli/ed, not fringed, developed from 

 a pedicelled sack. IVFale very different from the larger female. 



HALIPHRON. Arm only known. With bell-shaped e.ups, having lily- 

 like borders. 



