88 



A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



but all are badly worn and the fifth has apparently lost the apex since the original 

 description. The tooth figured by Cope (43) is the last of the series and is of little 

 diagnostic value, as the posterior teeth in all members of the family are of similar form. 



Desmatodon hollandi Case. (Plate 8, figs. 2 and 3.) 



Characteristic specimen: The type, No. 1938 Museum of Carnegie Institute. 

 Aside from the teeth described as typical of this genus, there are several chevron 

 bones belonging to an animal of larger size. Whether these belong to the genus 

 Desmatodon is uncertain; they may indicate an animal more closely related to 

 Diadectes, as they have the form and size of the chevrons of Diadectes phaseohnus. 

 The largest one has a length of 51 mm. 



Fig. 33. 



A. Lateral view of skull of Bolbodon tenuiietius. x J. No. 4375 Am. Mus. n, nasal; 



/, lachrymal; m.v, maxillary; pmx, premaxillary; pf, prefrontal. 



B. Lateral view of skull of Bolosaurus striatum. X* No. 4686 Am. Mus. fm, foramen 



magnum; j, jugal. 

 C Lower view of skull of Bolosaurus siriatus. X*. No. 4685 Am. Mus. pi, palatine; 

 pt, pterygoid; bs, basisphenoid; bo, basioccipital. 



The form of the teeth is intermediate between those of Bolbodon and Diadectes, 

 as is shown in the accompanying figure (fig. 34). The various forms can not be 

 regarded as phylogenetically connected, but represent different stages in an adapta- 

 tion to a purely herbivorous diet. 



These fossils are of peculiar interest because of the low geological horizon in 

 which they were found. Mr. Raymond, the discoverer, writes of them as follows: 



"The bones are from the upper part of the formation which I. C. White has 

 named the Pittsburgh Red Shale (Geol. Survey West Virginia, vol. II, p. 263). 

 This formation is usually from 100 to 125 feet thick in the vicinity and consists 

 of red clays and red and yellow sandstones. At the top there is a bed of almost 

 structureless clay, which varies from 18 to 40 feet in thickness. At Pitcairn the 



