180 



First costal plate . . 

 Second costal plate. 

 Third costal plate. . 

 Fourth costal plate. 

 Fifth costal plate . . . 

 Sixth costal plate . . 

 Seventh costal plate 



Length. 



Inches. 



c 



8. 



7 



Depth 



internally. 



Lines. 



29 

 22 

 21 

 23 

 22 

 18 

 10 



Depth 



externally. 



Lines. 



32 



38 

 26 

 2G 

 33 

 42 

 21 



REMAINS OF TtilONYX OF UNDETERMINED SPECIES. 



Small fragments of Trionyx shells, from the Bridger Tertiary strata, exhib- 

 iting a different kind of surface-marking or sculpture from that of the specimens 

 referred to the preceding species, probably indicate others, or, perhaps, differ- 

 ent genera. 



A specimen found by Dr. Carter at Dry Creek, and represented in Fig. 11, 

 Plate XVI, is an outer fragment of a costal plate. It is not pitted as in 

 Tronyx guttatus, but is crossed obliquely by coarse ridges with the intervals 

 occupied by a lattice of narrower ridges. Probably the specimen may belong 

 to a species of Anosteira. 



Another fragment of a costal plate, from Little Sandy Creek, is represented 

 in Fig. 12 of the same plate. This specimen differs from the former in being 

 crossed by widely separated ridges, with the intervals finely pitted. 



Other specimens exhibit slight differences from the foregoing and from 

 those of Trionyx guttatus, but are too imperfect to enable one to form any 

 idea of their relationship. 



Order Lacertilia. 



■ The lizards have vertebrae with concavo-convex bodies, and have the teeth 

 co-ossified with the jaws. The skin is furnished with horny or bony scales. 

 True lizards, allied to the existing monitors, iguanas, and chameleons, appear 

 to have been abundant and of varied character in the ancient Wyoming fauna. 

 Few remains of these animals, described in the succeeding pages, have been 

 submitted to my inspection, but Professor Marsh has indicated and briefly 

 described twenty-one species of five extinct genera from fossils obtained 

 by him from the Bridger beds. 



