52 Tnr. wasatch and BRrooER faun^. 



Twin Creek. He gave .a meager description of the species, but quite neg- 

 lected to describe the genus, on which account its affinities remain unknown. 

 The presence of several tubercles mentioned by Marsh indicates that it is 

 a different species at least from the Xiphotryyon acutidens. 



GINGLYMODL 



Cope, Proceedings American Association for tbe Advancement of Science, 1H71, p. 330. 



Physostomous Actinopteri, with a praecoracoid arch and a coronoid 

 bone of the mandible. Vertebral centra opisthocoelous. Parietal bones in 

 contact ; pterotic and opisthotic bones absent ; pectoral fin with mesoptery- 

 gium and five other basal elements 



This order contains as yet but one family, the Lepklosteklce, which em- 

 braces three genera, the recent Litliolepis and Lepidosteus, and the extinct 

 Clastes. The existing species, as is well known, are confined to the rivers 

 and lakes of North America, while the extinct forms occur in both Europe 

 and North Ameiica. The earliest appearance of this type in geological 

 history yet known was in the Laramie or Upper Cretaceous epoch in North 

 America. Individuals of one species, Clastes occidentalis Leidy, were very 

 numerous at that period. During the Wasatch or Suessonian in North 

 America, they were equally abundant, and I have described two species 

 from this honzon in New Mexico. Species and individuals are plentiful in 

 the Bridger beds, as indicated in the following pages, but in the various 

 tracts of the White River epoch they are absolutely wanting.* Tliey do 

 not occur in the Loup River deposits east of the Rocky Mountains, and 

 only reappear in the interior of the Continent in the present period. 

 On the other hand, the family is represented in the marine Miocene beds 

 of the Atlantic seaboard by the genus Pneumatosteus Cope, of which a single 

 speciesf has been foimd in North Carolina In Europe tlie Lepidosteidce 

 make their appearance at nearly the same horizon as in America, Lemoine 

 having obtained Clastes from the lowest Suessonian (Chalons-Sur-Vesle), 

 and Gervais having determined it from the Upper Suessonian. 



* ProcecdiniKS Aiiu'rican Pliiloso]iliiciil Socioty, 1877, p. 9. 

 t Proceedings Americau I'bilusoiiliical Society, 1669, p. 242. 



