128 



THE EXTINCT BATKACIIIA, EEPTILIA 



nals, and thinner edged more recurved marginals. The size of the marginals is similar 

 to those of the last, while the mesosternal element is larger. The scutal sutures are 

 better preserved than in the type of E. petrosus, nevertheless none are preserved on the 

 lower surfaces except that Which divides the mesostemum longitudinally throughout. 

 The vertebral scuta are § as wide as long, and have longitudinal borders, winch are 

 scarcely produced at the junction with the intercostal suture, and are otherwise somewhat 

 irregular. The carapace is swollen in an interrupted line bordering tin; vertebral scuta 

 externally, leaving the median parts of these smooth. The marginals are also slightly 

 swollen just within the costal-marginal sutures. The marginal bones are concave exter- 

 nally, and thickened inferiorly at some distance within the margin. That from the bridge 

 is angulated at one extremity at 45°, at the other less. The union of the hyostcrnals 

 behind and with the mesosternal behind, is by a groove and keel suture. The mesosternal 

 is much thinner anteriorly than posteriorly. 



Length heads of four costals, 

 " vertebral, 



Width 



Length hyosternal, 



" from mesosternal, 



Thickness " at " 



" " posteriorly, 



Length vertebral scutum, 

 Width 



la. 



4.375 

 1.06 

 1. 



2.4 

 1.8 



.65 



.7 

 2.8 



.75 



From the upper Green Sand Bed, Cretaceous N. J., at Hornerstown, N. J. 



EMYS PBTROLEI, Leidy. 

 Proceed. Academy, LS58, Postpliocene, Harden Co., Texas. 



A very distinct species, probably of the more terrestrial type of the genus, as Che- 

 lopus, etc. 



A DOG US, Cope. 



Emydoid tortoises in which the rib heads of the posterior costal bones are represented 

 by a rudimental lamina, and the anterior by a crest or truncate ridge in addition. Verte- 

 bral scuta narrow; external surfaces smooth or nearly so. 



Name from A privative and j„,x,^ rafter (i e., rib head). 



This genus, formerly characterized, differs from Emys in the absence of costal capitula 

 of the costal plates of the carapace, a feature pointed out by Leidy in the type species. 



