494 Bulletin American Museum of Natural History. [Vol. XIX, 



caudals 5-1 1. These chevrons have an entirely different form 

 from the deep, narrow chevrons in G. clavipes. 



Both ossa innominata, as well as the entire dorso- and 

 caudo-sacral complex, are preserved. 



Generic and Specific Characters. 



The hexagonal osseous plates of the carapace of this species 

 resemble those figured by Leidy {op. cit., pi. iv, fig. 9 ; pi. vi, fig. 

 i) as 6^. petalijerus, but differ specifically in: (i) the relatively 

 large size of the central area ; (2) the smaller size and irregular 

 form of the peripheral areas; (3) the shallowness of the cir- 

 cular and radiating grooves. 



As regards generic distinction, this animal is very primitive 

 and simple in its tail structure, which strongly suggests that 

 of PropalcEohoplophoriis and other Santa Cruz (Miocene) t3'pes, 

 but it appears to show some degeneration in the sculpturing 

 of the carapace plates, in which the central and marginal 

 areas are not so sharply defined as in G. pctalifents, Panoc- 

 thns, and other types. The imbricating lateral plates suggest 

 those of Panocthus. The shallow caudal chevrons are rather 

 like those of Sclerocalyptns (Hoploplwrus) than the deep 

 chevrons of Glyptodon. The general shape of the carapace is 

 also rather like that of the Sderocalyptus type than that of 

 Glyptodon. 



