1896.] FISHES OF THE FAMILX GONOBHTNCHID^. 501 



became the type of the genus Sphenolepis of Agassiz ', and was 

 then referred to the Esocidae. The Montinartre specimen described 

 and figured by Ouvier was also placed in the same genus under the 

 name of Sphenolepis cuvieri • and since that date both these fishes 

 seem to have been always quoted as related to the genus Esox. 



A recent examination of the specimeus of these two fishes in the 

 British Museum has now convinced the present writer tliat Cuvier's 

 original comparison of Sphenolepis cuvieri with Oonorhynchus was 

 correct ; that Sphenolepis squamosseus certainly belongs to the same 

 genus ; and that both these fishes are generically identical with 

 Notoc/oneus osculus from the freshwater Green Eiver Shales (Eucene) 

 of Wyoming, U.S.A., which Professor Cope referred to the 

 GonorhynchidiB eleven years ago"". As the ouly surviving genus, 

 Gonorhynchus, seems to be exclusively restricted to the seas border- 

 iug Japan, South Africa, Australia, and New Zealand, the discovery 

 of an extinct freshwater ally both in Europe and America is one of 

 some interest. It is thus important that the principal osteological 

 characters of the known fossils should be clearly stated to justify 

 the comparisons made. 



1. NoTOGONEus oscuLrs. (Plate XVIII. figs. 1, 2.) 



1885-86. Notor/oneus osculus, E. D. Cope, Amer. Nat. vol. xix. 

 p. lOyi ; Mem. Nat. Acad. Sci. vol. iii. p. 163, pi. with figs. 4, 5. 



Formation and Locality . Green Eiver Shales (Eocene) ; Wyoming, 

 U.S.A. 



The North-American form Notogoneus osculus has already been 

 well described by Cope, who also publishes a diagrammatic figure. 

 A beautiful new specimen, however, lately acquired by the British 

 Museum, permits the determination of a few additional features. 



The head in this fossil, shown of the natural size in PI. XVIII. 

 fig. 1, is exposed directly from the side, and thus does not exhibit 

 the hinder part of the cranial roof, which is fortunately well seen 

 in the original specimen figured by Cope. The large and character- 

 istic right frontal bone (fr.) is distinct, while the upper part of the 

 otic region (ot.) is shown to be well ossified, and is evidently not 

 entirely covered by the squamosal. The much-expanded hyoman- 

 dibular {hm.) is exposed, except at its lower end ; but the other 

 elements of the suspensorium, as also those of the pterygo-palatine 

 arcade, are too much crushed and fractured to be distinguishable. 

 The articulation for the mandible, however, is distinct below the 

 front border of the orbit, and portions of both rami are preserved, 

 that of the left side thrown upvi'ards a little above the right ramus. 

 Though imperfect the bones here indicated can readily be deter- 

 mined by reference to the corresponding elements in the existing 

 Oonorhynchus (PI. XVIII. fig. 5). The articulo-angular bone (ag.) is 

 almost tan-shaped, extending upwards immediately in front of the 

 articulation into a large, bluntly-pointed process. The dentary (rf.) 

 is much larger than the latter element, truncated in front, with 

 very short oral border, and rising into an enormous upwardly- 



1 Poi83. FosB. vol. T. pt. ii, (1844), p. 87. 



' American Naturalist, vol. xix. (1885), p. 1091. 



