1912.] NATURAL SCIENCES OF PHILADELPHIA. 437 



form intended beyond any manner of doubt. It is interesting to 

 observe that Steenstrup himself affirms entire ignorance of the true 

 generic position of 0. sloanii, although Hoyle in the work cited 

 referred it doubtfully to Todarodes. More recently Pfeffer (1900) 

 has come to the conclusion that the two forms are identical and has, 

 moreover, reduced them to subspecific rank under the Atlantic 

 O. sagittatus. If these premises are correct, the rejection of the name 

 pacificus -m favor of the prior sloanii follows as a matter of course, 

 an arrangement which has since been followed by Hoyle (1909) and 

 by Wiilker (1910), and is therefore adopted in this paper. To the 

 present writer, however, this interpretation does not appear by any 

 means conclusive. In the first place, the description of Gray when 

 judged by modern standards is at best incomplete, and an examina- 

 tion of his type or even of further South Pacific material may yet 

 reveal that he overlooked characters of sufficient importance to 

 delimit this race from the Japanese form as completely as the latter 

 now appears to be separated from its Mid-Pacific (Hawaiian) con- 

 geners. In the same connection another small item of evidence 

 should not be overlooked: so careful an observer as Verrill (1881, 

 p. 386) relates that a Tasmanian specimen referred by him to 0. 

 sloanii lacks the foveola at the apex of the funnel groove so charac- 

 teristic of 0. sagittatus, pacificus, and hawaiiensis. In any case, the 

 specimens now before me are most certainly identical with the true 

 0. pacificus as described and figured by Steenstrup and Hoyle, 

 whether the latter eventually prove distinct from sloanii or not. 



A key to the various known races of typical Ommastvephes, con- 

 structed on the same general plan as that utilized by Pfeffer, is 

 accordingly offered as follows : 



Sucker-bearing portion of the tentacle comprising more than f of the 



total length (Atlantic species) sagittatus. 



Sucker-bearing portion of the tentacle comprising distinctly less than 



f of the total length (Pacific species) 1 



f Median upper tooth of the horny rings of the suckers on the 



, sessile arms obviously the largest hawaiiensis. 



' No single tooth of the horny rings noticeably larger than the 

 others sloanii 



Most recent authors follow Pfeffer in regarding sloanii as a sub- 

 species of sagittatus, but despite the small differences I cannot see 

 that anything is to be gained by the use of the trinomial, especially 

 since truly intergrading forms are not yet known to occur. 



