CEPHALOPODS OF WESTERN NORTH AMERICA. 27 1 



CLASSIFICATION. 



Although the collections examined contain a fair supply of novel forms, the interest 

 of these is mainly zoogeographical and as a rule they have little light to throw upon 

 the broader problems of morphology and interrelationship. Consequently I have 

 advanced no very new ideas of classification, but have been quite content to follow the 

 general lines laid down in the various works of Hoyle, or in some cases that represented 

 with certain slight modifications in Pfeffer's indispensable Synopsis (1900) and in the 

 Nordisches Plankton Report (1908) of the same author. 



For convenience in rapidly referring to any of the species here described, the follow- 

 ing key is offered. It is perforce more artificial than natural, and it must be further 

 remembered that the likelihood of the occurrence of forms not previously known to the 

 region is still so great that no attempt should be made to rest an identification upon the 

 key alone. 



KEY TO THE CEPHALOPODA KNOWN TO INHABIT THE WESTERN COAST OF NORTH AMERICA. 



I. Tentacles absent; suckers sessile, without a homy ring. (Octopoda.) 



I. A pair of lateral oar-shaped fins present; suckers in a single row. (Cirroteuthidse.) 



2. Dorsal cartilage saddle-shaped; mantle opening wide Cirroteuthis macrope, p. 273. 



2'. Dorsal cartilage horseshoe-shaped (?); mantle opening very 



small Stauroieuthis sp. ?, p. 274. 



1'. No fins. 



3. Aquiferous pores present on the head; female with an exter- 



nal shell; hectocotylus involving the entire third arm of 



the left side and separable -1 rgonaiila pacifica, p. 273. 



3'. No aquiferous pores; no external shell; hectocotylus con- 

 fined to tip of arm. (Polypodidae.) 



4. Suckers in a single row; body sfjft Eledonella heathi, p. 276. 



4'. Suckers in two rows; body fairly firm. {Genus Polypus.) 

 5. .\. jirorainent pigmented spot in front of each eye; 



hectocotylus very minute Polypus bimaculatus, p. 278. 



5'. No definite oculations. 



6. Dorsal arms notably the longest; body with a pe- 

 ripheral fold of the integument P. letoderma, p. 288. 



6'. Dorsal arms not usually the longest; body without a 

 peripheral fold. 

 7. Hectocotylized portion of arm relatively moderate 

 in size — one-ninth to one-twentieth the total 



length P. hongkongensis, p. 280. 



7'. Hectocotylized portion of arm extremely large — 

 one-fifth to one-eighth the total length. 



8. Surface papillfe small, simple P. gitberlianus, p. 284. 



8'. Siu^ace papills large, soft, stellate P. californicus, p. 286. 



II. Tentacles present; suckers stalked, usually provided with a 



homy ring (Decapoda.) 

 I. Eyes covered by a continuous membrane. (Myopsida.) 

 2. Body short, rotmded, with ovate lateral fins; dorsal margin 



of mantle free from head ; both dorsal arms hectocotj'lized . Rossia pacifica, p. 290. 

 2'. Body elongate, pointed, with subterminal triangular fins; 



left ventral arm hectocotylized Loligo opalescens, p. 294. 



