AND REPTILIA OF NORTH AMERICA. 275 



EURYTHORAX, Cope. 



Established on a large thoracic shield of peculiar form. It is a median, and 

 exhibits broad smooth surfaces for the contact of the overlapping margins of the 

 lateral plates. The form is subround with a large excavation from the posterior mar- 

 gin on each side. The narrowed portion left has a convex outline. Sculpture none. 

 The form resembles remotely the corresponding scute of Tuditamis punctidatus, the 

 posterior narrow face representing the xiphisternal process of that species. 



EURYTPIORAX SUBL^EVIS, Cope. 

 Proceed. Amer. Philos. Soc, 1871, 177. 



The specific characters expressed by this shield are best perceived in the meaiurements : 



M. 



Length, .0715 

 Greatest -width (imperfect), .078 

 Width of lateral concavity, .039 



Some delicate radiating grooves are seen on the exposed surface, but they are very shallovr. They are not 

 visible on the faces of contact. 



This repi-esents one of the largest species of this fauna, having pertained to an animal of probably four feet in 

 length, perhaps longer. It will be desirable in future to compare it with the corresponding part of the Tuditamis 

 Jiuxleyi, though the latter, so far as known, is the smaller species. 



COLOSTEUS, Cope. 

 Transac. Amer. Philos. Soc, 1809, XIV., p. 22. 



COLOSTEUS SCUTELLATUS, NewUrry. 



Cope, Proceed. Amer. Philos. Soc, 1871, p. 41. Pygopterus scutellatus, Newberry, Proceed. Acad. Nat. Sci., 

 Philadelphia, 1850, p. 98. Colosteus crassiscutatus, Cope, Transac. Amer. Philos. Soc, XIV., 1869, 23. 



COLOSTEUS FOYEATUS, Cope. 

 Transac. Amer. Philos. Soc, 1859, XIV., p. 34. 



COLOSTEUS PAUCIRADIATUS, Cope, Sp. Nov 



Established on median and lateral pectoral plates of two individuals, the latter of which I formerly referred 

 to the C. scutellatus. It belonged to a larger specimen than either of the pi'eceding, and is distinguished by the 

 paucity and weakness of its ridges These are entirely transverse on the posterior third of the length, but are inter- 

 rupted and irregular on the median portion ; the anterior third is almost smooth. 



The lateral shield is little larger than the largest of C. scutellatus, but resembles the median plate in its low 

 and distant carina3. An arc drawn at about the middle of a radial line from the outer angle ci'osses about eleven of 

 these ridges ; in C. scutellattts, twenty in the same space. 



The median plate is pyriform with the posterior angle little produced, and the anterior not narrowed and 

 rather short. The lateral shield is a right angled triangle, the inner or thin edge concave posteriorly, the posterior 

 convex. 



M. 



Length of median, 0.003 

 Width " " .040 

 " lateral behind, .0243 

 Length of lateral, .045 



