116 



MEMOIRS OP THE CARNEGIE MUSEUM 



an individual having tlie same proportions as the type, and shows on the dorsal 

 surface the triradiate shape of the entoplastron (See Fig. 4, 1). The entoplastron 



Fig. 4. Anterior lobes of Baena inflata. 1, and :?, superior and inferior views of C. M. No. 3137, ent., 

 entoplastron; hum., humeral scute. S, inferior view of anterior lobe of C. M. No. 3442. AU figures one-fourth 

 natural size. 



has a length of at least 50 mm.; a width of 44 mm. Transversely the lower surface 

 of the lobe is broadly convex. On the dorsal surface immediately posterior to the 

 anterior border the bone is scooped out by a shallow transverse depression. The 

 lateral borders are bevelled off almost perpendicularly, while in front the border 

 is rounded. The bone along the borders has a thickness of 13 mm., in front of the 

 center of only 9 mm., at the middle on the posterior broken border of 21 mm. 



4. Baena gigantea sp. nov. 

 Plate XX, figs. 1 and 2; text-figs. 5, 6, and 7. 



Type: C. M. No. 3441, consisting of nearly a complete shell. The carapace 

 lacks portions of the posterior margins on either side of the middle, a small section 

 of the right anterior border, and the peripherals of the right side above the bridge. 

 The plastron has the greater part of the posterior lobe missing. Collected by 

 Earl Douglass, in 1915. 



Locality: Wagon-hound Bend, on White River, Uinta County, Utah. 



Horizon: Lower part of Horizon B, Uinta formation. Upper Eocene. 



The type of the present species is the largest species of the genus as yet dis- 

 covered. It is estimated that the carapace had an axial length of about 535 mm. 

 The greatest width, which is near the center, is about 420 mm. The bones of the 

 carapace are all thoroughly coossified and only the sutures defining the right half 

 of the mesoplastron can be detected and then only with difficulty. The shell is 

 oval in outline, in this respect resembling Baena clara Hay, though the oval is 

 somewhat more elongate than in that species. The carapace has been slightly 

 crushed on the right side, as may be seen by examining Plate XX, fig. 1. 



The front of the carapace is decidedly projecting. The missing posterior 



