454 HAY— A FOSSIL SPECIMEN OF IMay 23, 



It will be observed tbat the last two skulls differ from eaeh other 

 about as much as the second differs from the fossil. 



The same three skulls furnish the following measurements. 



l'ra7os R. 

 Meisurements. skull. No. 3769. No. 3444. 



Snout to occipital condyle i83± i/O 177 



Snout to hinder end of supraoccipital process.. 262± 236 226 



Least width pterygoid region ;ii 29 29.5 



Outside to outside of quadrates 187 166 163 



Distance between hinder ends of cutting edges 



of upper jaws 142 128 126 



Width in front of ear cavity 218 195 191 



Width of temporal arch where narrowest 77 71 68 



Orbit to excavation of postorliital arch 87 82 80 



Horizontal diameter of orbit 32 30 32 



Distance between fronts of orbits 55 50 53 



Fig. I of Plate XIX represents the fragment of the carapace that 

 accompanied the skull. This is reduced to five twelfths the natural 

 size. It consists of a part each of the third and fourth costal plates, 

 and of a part each of the sixth and seventh peripherals. On these 

 parts are present areas rei)rcsenting the outer and hinder angle of 

 the third costal scute, a little of the third and the whole of the 

 fourth supramarginal scutes, the wdiole of the eighth marginal scute 



Fk;. I. Sectiiin of rim of carapace bclwecn .-^ixth and seventh peripherals. 



and a ])art each of the seventh and the ninth. These structures are 

 almost identical with the ccn-responchng ones of a mounted specimen 

 of the species in the United States National Museum. 



Fig. I represents a transverse section of the rim of the carapace 

 taken between the sixth and the seventh peripherals. 



