120 MEMOIRS OF THE CARNEGIE MUSEUM 



5. Baena platyplastra sp. nov. 

 Plate XVIII, fig. 2; text-fig. 8. 



Type: C. M. No. 3227, consisting of a plastron lacking the anterior portion 

 of the anterior lobe, matrix cast of the carapace, at either end of which remain a 

 few fragmentary parts of the carapace. Collected by Earl Douglass and J. F. 

 Goetschius, August 5, 1908. 



Locality: Northeast of Well No. 2, Uinta Basin, Uinta County, Utah. 



Horizon: Horizon B, Uinta formation. Upper Eocene. 



The type specimen represents one of the larger species of the genus. It is 

 distinguished from all other described species of Baena by the extremely flat and 

 thin plastral bones with sculptured inferior surfaces. Its large size and the absence 

 of a median emargination on the posterior lobe are features which also assist in 

 distinguishing this species. 



The ornamentation of the plastron consists of low ridges and shallow furrows, 

 the former being short, sometimes straight, but usually bent or anastomosing. 

 The effect of the whole may be best expressed as resembling a coarse, shagreened 



Fig. 8. Plastron of Baena platyplastra, C. M. No. 3227. Type, one-fourth natural .size. 



leather. The sutures in the type have all coalesced, but their courses are indi- 

 cated by ridges crossing them at right angles. These cross-ridges are especially 

 pronounced on the median suture between the axillary notches. 



