160 



The episternals at their uiiier border measure 1 inch ia length ; at their 

 posterior extremity 10 lines. 



The entosternal bone is 2J inches fore and aft, and 2f inches wide. 



In the better preserved of the two specimens the plastron presents the 

 irregularity of having the left hyposternal and xiphisternal near half an inch 

 more produced forward than npon the right side, as seen in Fig. 2, Plate XII. 



Measurements of the remaining sternal bones are as follows : 



Lines. 



Length of right hyosterual internally 30 



Length of left hyosterual internally 25 



BreadtJi of hyosternals at middle 58 



Length of hyposternals internally 34 



Breadth of hyposternals at middle 52 



Length of right xiphisternal internally 34 



Length of left xiphisternal internally 40 



Breadth of anterior border 24 



Measurements of the scutes are as follows : 



Lines. 



Length of gular-humeral scute internally 28 



Breadth of gular-humeral scute posteriorly 26 



Length of pectoral scute internally 18 



Breadth of pectoral scute posteriorly 36 



Length of abdominal scute internally 29 



Breadth of abdominal scute posteriorly 28 



Length of femoral scute internally 26 



Breadth of femoral scute posteriorly 22 



Length of caudal scute internally 27 



Axillary scute obliquely from within outward 32 



Axillary scute at posterior border 13 



Middle scute of sternal bridge fore and aft 17 



Middle scute of sternal bridge at middle, transversely 25 



Inguinal scute fore and aft 32 



Inguinal scute at anterior border 13 



Inguinal scute at middle between prominent angles , 29 



BAENA. 



By this name I have distinguished a remarkable genus of turtles, indicated 

 by remains in the Bridger Tertiary beds. It partook of characters of the 

 snappers or chelydroids, the terrapins or emydoids, and the sea-turtles or 

 chelonioids. The specimens upon which the genus is founded consist of shells, 

 which are mostly so much crushed and distorted as to render it somewhat 

 uncertain as to their exact original and perfect form. They were apparently 

 about as prominent as in our snapper, and had nearly the same outline of shape. 

 Tlie middle of the carapace is not depressed as in the latter, but is somewhat 



