440 THE FUR SEALS OF THE PRIBILOF ISLANDS. 



36. Osm^ruB thaleichthys Ayres. 



Several young specimens from Nushagak Kiver were referred to this species by 

 Dr. Gilbert. There is no other record of it from Alaska, and these northern examples 

 may prove distinct from the Californian species. 



37. Mesopus olidus (Pallas). 



Petropaulski Harbor, Shana Bay, Iturup Island. Also recorded from Petropaulski 

 by Stejneger. 



The posterior insertion of the ventral lins has been exaggerated in this genus. 

 Instead of being belovr or posterior to the middle of the dorsal, we find it approxi- 

 mately under front of dorsal, varying from slightly in advance of this point in the 

 young to slightly behind ia the adults. 



Specimens from the two localities given above diflTer somewhat from each other in 

 length of dorsal and in scale formula. Those from Petropaulski have 65 to 67 scales, 

 and 9 or 10 developed rays in the dorsal; from Iturup Island, 57 to 60 scales, and 8 or 

 9 rays in the dorsal. We do not venture to separate the two lots on the basis of our 

 limited material, although the distinctive characters are constant in_ about 20 speci- 

 mens of each. In M. oligodon Kner {=M. olidus) from Decastris Bay there are said 

 to be about 60 scales, but the figure of Kner shows 68. Representatives of this 

 species from St. Michael, Alaska, are reported as having 56 to 60 scales, thus agree- 

 ing with those from Iturup. In the formerj however, the paired fins, appear to be 

 longer. M. pretiosus from southeastern Alaska and Puget Sound differs from M. 

 olidus from Petropaulski no more than the latter do from Iturup or St: Michael 

 specimens here called M. olidus. It seems probable that we are dealing either with 

 one species or with three or four. 



The generic name Mesopus was regularly proposed, the genus characterized, and 

 type specified on page li, Proceedings Academy Natural Science, Philadelphia, 

 1862. On the following page, in a key to the genera, there appears in its place the 

 name Hypomesus. In the index to the volume the name Mesopus alone appears. 

 There is nothing in the article to indicate which of the names was the final choice of 

 the author. Even were that evident, we consider it safer to conform strictly to the 

 law of priority without permitting any exceptions. 



38. Leuroglossus stilbius Gilbert. 



Recorded from near Unalaska in 351 to 406 fathoms. 



39. Therobromus oallorhmi Lucas, new species. Seal fish. (Plate XLVII.) 



Among the fishes obtained from the stomachs of fur seals by Messrs. Townsend 

 and Alexander were many examples of an undpscribed isospondyloiis fish related to 

 the Argentinidae, although possibly representing a new family. For this species the 

 name Therolromus callorhini is proposed, from the fact that it is so extensively eaten by 

 the fur seal. Owing to the tenderness and small size of this fish, it is so quickly acted on 

 by the gastric juice that nothing but bones remained of the many hundred specimens 

 that were seen and while evidently common, it can be described only from the 

 skeleton, No example of Argentina being available it can only be said that Thero- 

 hromus differs from that genus in the shape and proportions of the component bones 

 of the jaw and gill covers, and that it finds its nearest relative in Mesopus, from 

 which it may be readily distinguished by its cranial characters as well as by the small 

 number of vertebrae, 26, 22 as against 32, 22. 



