42 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



central point. Its section at the base is slightly angulate. The two other premaxil- 

 lary teeth are much smaller, the third quite minute and with a sharp apex. 



"There are three maxillary teeth separated by rather wide interspaces, anterior 

 to the large tooth, which gives character to the genus. The latter is abruptly large, 

 but not equal in dimensions to the large first incisor. Posterior to it the maxillary 

 teeth are closely placed, and with obtuse crowns. They commence very small, and 

 increase in size posteriorly. At a point where the palatine or ectopterygoid, as 

 the fact may be, joins the maxillary, the tooth-bearing surface is wide, and supports 

 four rows of small, obtuse-crowned, spaced teeth of equal size. This dental patch 

 is triangular, with its long angles extending anteriorly and posteriorly. The latter 

 angle terminates a little posterior to the middle of the orbit. The teeth have a small 

 axial pulp cavity, and the dentine is perfectly simple. 



"The head sculpture is well defined, and is reticulated in pattern. 



"Measurements. 



"Length from the end of muzzle to the posterior border of the orbit 0054 



Transverse diameter of the orbit . 016 



Transverse diameter of interorbital space 020 



Length from the end of muzzle to the orbit 034 



Vertical diameter of nostril 008 



Vertical depth of maxillary in front 013 



Length of first premaxillary tooth 0065 



Transverse diameter of do . 00 3% 



Distance between first incisor and large maxillary tooth 013 



Distance from large maxillary tooth to posterior angle of dental patch . .024 



Width of dental patch 0105 



Elevation of a posterior tooth 0015 



"This species is intermediate in size between E. ordinatus, which is small, and 

 the E. aguti, which is large. In its disproportionate inequality in size of the teeth, 

 it differs from the latter; while the former has larger orbits and a different sculpture, 

 besides having half the linear measurements. The sculpture of the E. ordinatus 

 is in parallel ridges, inclosing minute punctiform pits between them." 



Later, in 1896, Cope added to his original description: 



"The long maxillary tooth nearer the nostril than the orbit. Sculpture reticu- 

 late. Interorbital and parietal sculpture reticulate; interorbital width 20 mm; 

 interior jaw teeth with rounded crowns." 



Revised description: Smaller. Median upper incisors not larger than the others; 

 incisors increasing in size regularly toward the median line. The third, fourth, and 

 fifth maxillary teeth larger than the others. 



The specimen, No. 4333, called by Cope Pariotichus (Ectocynodon) incisivus, 

 can not be distinguished from the one called P. aguti, No. 4344, and it seems ad- 

 visable to unite the two under the earlier name. The type specimen of aguti has 

 been deprived of the bone on the upper surface, so that the character of the sculp- 

 ture can not be made out. The diameter of the orbit is given as about equal to the 

 interorbital width; this is true of the horizontal diameter of the left orbit, but not of 

 the right nor of the vertical diameter of either. Due to the crushing the specimen 

 has suffered, the diameters are all notably different. The outlines of the skulls can 

 not be compared, for the same reason, nor can the character of the posterior maxillary 

 teeth, as they are not shown in aguti. On the other hand, both of these specimens 

 have the median incisor greatly enlarged and the fourth or fifth maxillary tooth con- 

 siderably enlarged. The two specimens have approximately the same size and 

 proportions. These points connect the two specimens and separate them from all 

 others. 



