NORTH AMERICAN PLESIOSAURS 729 



as in Polycotylus. The generic name is derived from the belief 

 that there were but three bones in the epipodial row. Beyond 

 these connected series of bones there is another, and still a third 

 includes the extreme tip of the paddle. In the first digit there are 

 actually preserved ten phalanges, in the second twelve, and in the 

 third fourteen — this last is the longest. The second digit could 

 not have had less than fifteen and the third twenty. The three distal 

 phalanges of the first digit seem to have been imperfectly ossified, and 

 are closely related to, if not co-ossified with, the second digit. So, 

 also, the distal four phalanges of the fifth digit are united, and are 

 closely applied to the fourth digit, as are also the terminal three or 

 four of the second with the third. The terminal phalanges of the 

 third and fourth digits are flattened at the end, almost ungulate. 

 The paddles are remarkably long and slender. 



Trinacromerum anonymum Willi ston 



A specimen in the Yale Museum (No. 1129), collected in 1873 

 by the late Mr. Joseph Savage from the Benton Cretaceous of Kan- 

 sas "three miles south of the Solomon," is clearly identical with the 

 species which I figured and partially described under the provisional 

 name Trinacromerum anonymum, the type specimen collected by the 

 late Professor Mudge from nearly the same locality and doubtless the 

 same horizon in the Upper Benton. The species differs from the 

 type species in its much smaller size, less slender skull, the different 

 shape of the interclavicle and of the propodial bone. The Yale 

 specimen must originally have been an excellent one, comprising the 

 skull and vertebral column and portions of the paddles, but Hke so 

 many of the specimens of those early days it suffered in its collection. 

 The skull (figs. 9, 10), so far as it is preserved, bears a strong resem- 

 blance to T. osborni, but the attenuated portion of the face is shorter 

 and the symphysis of the mandibles much shorter. The under- 

 surface of the parietals with their attachments is clearly shown, and a 

 litde in front the opening into the deep median sinus or canal leading 

 to the pineal foramen 50"^"^ in advance is clearly seen. Two tongue- 

 like projections He close together, projecting apparendy as far forward 

 as the end of the projection, the under surface with longitudinal striae 

 Hke those of the upper surface. On each side there is a broad deep 



