Pacific Species of Hippoglossoides. 305 



body seems to be not higher, as Snyder gives, but the same 

 as in H. elassodon (10°/ o of the length to the base of caudal) ; 

 the number of rays in the dorsal is also not greater (cf. 

 Snyder, 1912, p. 139) than in this species. Only the lateral 

 line seems to form a more abrupt and higher arch ; but this 

 feature is highly variable, and one can find in Hippoglossoides 

 elassodon all the transitional stages. 



Studying now the Heterosomataof the Russian seas in the 

 Zoological Museum of the Imperial Academy of Sciences in 

 Petrograd, I have examined the large material on Pacific 

 forms of Hippoglossoides collected by different Russian expe- 

 ditions during the last ten years, and I have re-examined 

 also my former material. This study brings me to the con- 

 viction that in the Pacific Ocean there is, as in the Atlantic, 

 only one well-defined species of Hippoglossoides, with three 

 highly variable subspecies. 



The material examined consisted of forty-six specimens of 

 different sizes ; one part of these was accurately measured on 

 a detailed scheme, and percentage values were calculated. 



By these detailed studies I could not find the limits of 

 three species which seemed to me to be well defined in my 

 first examination twelve years ago. All these species — 

 Hippoglossoides elassodon, H. robustus, and H. dubius — were 

 represented in our collections, but they were so connected 

 through different transitions that it was not possible to separate 

 them from one another. They must therefore be regarded 

 not as separate species, but as subspecies (or varieties) of one 

 species — Hippoglossoides elassodon, Jord. & Grilb. 



The most characteristic of these three forms is Hippo- 

 glossoides elassodon dubius, which is distinguished by the 

 strong, curved, canine-like teeth on the anterior part of the 

 premaxillaries and on the symphysis of the lower jaw ; but 

 the number and position of these teeth are the same as in 

 other forms — only they are more developed, sometimes twice 

 as long as the other teeth. All the other features formerly 

 considered by me as distinguishing characters lie within the 

 limits of variation of both the other forms. 



The number of rays in the fins of Hippoglossoides elassodon 

 dubius is also not characteristic ; we find in our collection 

 the following variation : — 



D. 77 81 83 84 85 87 90 rays. 



2 12 12 2 1 specimens. 



A. 57 62 63 65 66 67 rays. 



12 112 4 specimens. 



