296 



5. W. WILLISTON 



numerous ilia in the collections (I have seen about two score) 

 there is no indication of roughening for attachment to sacral ribs. 

 So far as was prudent the matrix has been removed about the 

 ilium; there are no indications of ossified pubis or ischium. The 

 proximal end of the right femur lies nearly in place opposite the 



A 



B C 



Fig. 3 — Trimerorhachis Integument. A, surface view, No. 1271. B, C, cross- 

 sections. No. 1208. All enlarged four times. 



acetabular surface of the ilium, directed outward; its distal end has 

 been lost from erosion of the matrix. 



The looseness and small size of the ilium and the probable 

 chondrification of the other pelvic bones are conclusive evidence, 

 if more were needed, that Trimerorhachis was an exclusively 

 aquatic animal, incapable of progression upon land. Are the 

 undifferentiated "sacral" ribs and their lack of connection with 



