1044 



CEPHALOPODA. 



KEY TO FAMILIES AND GENERA.* 



10 



11 

 12 



Suckers sessile, with no homy ring ; nor- 

 mally with 8 arms 



Suckers stalked, with a horny ring ; nor- 

 mally with 8 arms and 2 tentacles 



No ear-shaped fins ; mantle-aperture single 



An external shell 



No external shell 



Body firm, not soft and gelatinous 



Mantle connection consisting of either deep 

 grooves and ridge, or cartilaginous knobs 

 on the mantle and corresponding hollows 

 at the base of the funnel ; aquiferous 

 pores present ; hectocotylus involving 

 the whole arm, which is separable 



Mantle connection consisting of shallow 

 folds on hinder margin of funnel and shal- 

 low groove on the mantle ; no aquiferous 

 pores ; hectocotylus confined to tip of 

 arm, never free 



Funnel organ made up of three separate 

 portions ; mantle connection carti- 

 laginous ; an aquiferous pore at eithei 

 side of the siphon, none in the head 



Funnel organ composed of numerous longi- 

 tudinal lamellae ; mantle connection com- 

 posed of membranous folds, without 

 cartilage ; an aquiferous pore on either 

 side of the siphon and 2 in the head ; 

 hectocotylized arm on the right side 



Body 30 mm. or less in length, with one 

 ventro-lateral arm developed on an oval 

 sac and specially modified into a separable 

 hectocotylus, which is on the left side . . 



Suckers on the arms in 2 rows . . 



A broad fin on either side of the body, 

 rendering the outline heart-shaped 



No lateral fins, the third arm of right side 



hectocotylized 

 A spiral internal shell, protruding on the 



dorsal and ventral surfaces . . 

 No spiral shell 

 Eye covered by a continuous membranous 



lid 



Eye with a perforated lid 

 Body short, rounded, with separate ovate 



lateral or subterminal fins 

 Body oval or elongate, with tins either 



marginal or terminal 



Body short, saecular ; medio-dorsal margin 

 of mantle either continuous with head 

 or with cartilaginous connection ; right 

 oviduct absent ; one ventral or both 

 dorsal arms hectocotylized 



OCTOPODA 

 DECAPODA 



ARGONAUTID^;; ARGONAUTA 



9 

 2 



? 

 3 

 4 



ARGONAUTID.'E. . 



P( ILYPODID.E . . 



TREMOCTOPUS. 



ARGONAUTA <f . 



PINNOCTOPUS. 

 POLYPUS. 

 SPIRULID^E ; SPIRULA. 



MYOPSIDA 



OlGOPSIDA 



10 



11 



16 



12 

 13 



SEPIOLID.-E : SEPIOLA. 



AtVr Dr. lloyl.-. 



