1903.] Hay^ North American Cretaceous Fishes. 9 1 



Upper Cretaceous of Mount Lebanon, and L. elongaUis 

 (Agassiz), from the Senonian and Turonian of England. 



It seems not unlikely that of the species of Leptotrachehts 

 those having a long dorsal fin, L. triqueter, L. longipinnis, 

 and L. gracilis, will have to be separated as a distinct 

 genus, while L. armatus and L. hakelensis will be retained in 

 Leptotrachelus. 



MYCTOPHID^. 



MyctophidcB Jorlan and Evermann, Fishes of North and Middle 



America, 1S96, p. 550. 

 ScopelidcB of most authors. 



Leptosomus Marck. 



To this genus the present writer assigns the species from 

 the Niobrara of South Dakota, which Cope placed in the 

 genus Sardinius. The latter genus has the scales pectinated, 

 the pectoral fins with about 18 rays, the anal with about 20 

 rays, and about 45 vertebrae. The American species agree 

 with Leptosomus in having, so far as can be determined, 

 cycloid scales, narrow pectorals, a short anal, and about 30 

 vertebrae. Cope regarded Leptosomus as a synonym of Sar- 

 dinius, but Woodward properly separates it. The author last 

 named recognizes four species of this genus, L. guestphalicus 

 Marck and L. elongatus Marck, both from the Upper Cretaceous 

 of Westphalia, and L. macrouriis Pictet and Humbert, and 

 L. minimus (Agassiz), both from the Upper Cretaceous of 

 Mount Lebanon. 



Leptosomus nasutulus {Cope). 

 Plate IV, Figs. 4 and 5. 



Sardinius nasutulus Cope (E. D.), Bull. U. S. Geol. and Geog. Surv. 

 Terrs. IV, 1878, p. 70. — Woodward (A. S.), Cat. Foss. Fishes, 

 IV, 1901, p. 248. — Hay (O. P.), Bibliog. and Cat. Foss. Vert. 

 N. A. 1902, p. 391. 



Of this species there are in this Museum three specimens 

 as follows: The type No. 2512 (PI. IV, Fig. 4), No. 2513 

 (PI. IV, Fig. 5), and No. 2523. 



