r 





15 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



Original description of type: "The teeth are more completely molar in their 

 character than the species already described (£. alatui), being in the unworn con- 

 dition as broad across the crown as the latter is high. In the transverse direction 

 the crowns are two and a half times as long as wide. The extremities are rounded, 



and there is a median cusp extending across the crown; 

 on each side of the cusp, the face of the crown is slightly 

 concave. The enamel is strongly but finely wrinkled. 

 The series terminate abruptly in a tooth of half the 

 transverse extent of the penultimate. Length of space 

 occupied by the penultimate and ante-penultimate teeth 

 M. .021; length of base of the penultimate .010; width of 

 do. .024; elevation of crown, least .006; do. at cusp, .009. 

 "This species is larger than those heretofore de- 

 scribed, and the teeth are adapted for crushing harder 

 Fig. 1. —Two maxillary teeth of D'*&«" u A[ es having perhaps a use like those of Placodus or 



molaris. XI. Type No. 4347 Am. Mus. UUUICS '""' 6 F K . „ 



Pycnodus. It is called D. molaris. 

 Original description of paratype ("Proceedings American Philosophical Soci- 

 ety," l880, p. 47): . , . , , c -, 



"The molar teeth are wider in this species than in any species of the family yet 

 known The internal and external extremities of the crown are about equally wide 

 and equally elevated, and there is a low median cusp. A portion of the grinding 

 surface, both internal and external to the cusp, is horizontal; the surface of this 

 portion is wrinkled. The last molar is smaller than the others The inner border 

 of the maxillary bones forms a curved ridge on each side of the palate, which is 

 separated by a groove from the vomer. The latter forms a median keel at the an- 

 terior portion of the palate, where it supports two rows of small conica teeth. 1 he 

 palatines have their prominent internal edges juxtaposed as far as the transverse 

 line of the last molars. There they diverge a little, and extend as two nearly parallel 

 keels to a prominent angle on each side, opposite the middle of the zygomatic fora- 

 men There the inner borders cease to project, and are directed obliquely out- 

 wards to the inner extremities of the quadrate bones The external borders of the 

 pterygoids are more elevated than the internal. The median keel of the basi- 

 sphenoid arises between the internal angles of the pterygoids above mentioned, and 

 ceases before reaching the inferior border of the occipital condyle. 1 he external 

 border of the exoccipital is sigmoidally flexed. * 



"Measurements. 



"Total length of the skull al8 ° 



Width of the skull at quadrates I4 5 



Width of skull at origin of the zygoma n 5 



Width of skull at incisive foramen °5 



Length of dental series to posterior extremity of incisive foramen, on curve . . .090 



Diameters of third molar: 



. . 010 



Anteroposterior 



_ r 021 



I ransverse „,, 



Depth of mandible at fifth molar from behind °4» 



Revised description: The teeth in the type specimen are larger than in any 

 other of the specimens and it is probable that the larger skulls without the teeth 

 preserved belong here, as No. 4352 Am. Mus. Nat. Hist. Cope Coll. There is much 

 of the original description that is valueless and only the portion referring to the 

 teeth has been quoted. 



