239 



obtained by my expedition ; but the species is not determinable. The diam- 

 eter of the basis of the tooth is m .012. The long tooth of a species of 

 medium size was detected, the Enchodus calliodon, Cope (Enchodus sp., Cope, 

 Hayden's Survey of Wyoming, etc., p. 424), in the matrix beneath the verte- 

 brae of Elasmosaurus platyurus. 



Enchodus petrosus, Cope. 



Established on numerous portions of cranium and vertebras of one indi- 

 vidual, which had grown to the size of a twenty-five-pound muskallonge. 



The upper surface of the cranium is smooth, excepting along the inner 

 border of the pterotic, where a narrow ridge supports two rows of small 

 enamel tubercles. Numerous similar tubercles ornament the external face 

 of the post-frontal bone. 



The premaxillary has the anterior margin truncate obliquely upward 

 and backward ; its lower margin passing into the base of the single large 

 tooth. Alveolar surface elongate, posteriorly narrowed to an obtuse edge. 

 The maxillary exhibits both borders obliquely truncate, with sutural face ; the 

 alveolar aspect supports two teeth, one larger than the other. (No. 2.) 



The premaxillai-ies are very massive, and exhibit, on their upper faces, 



three oblique fossae ; the posterior transversely subdivided. External face 



smooth. 



Measurements. 



M. 



Length (distal end lost) 0.067 



Greatest width of the alveolar face 0.018 



Depth of the outer face 0.030 



Diameter of the basis of the tooth 0. 009 



Obtained by Professor Mudge from beds of the Niobrara epoch in 



Kansas. 



Enchodus dolichus, Cope. 



Represented by the premaxillary and adjacent parts of the maxillary 

 bone with teeth, of a specimen of one-tenth the size of the preceding, and 

 differing from it in the more slender proportions and the peculiar positions 

 of the teeth. 



The premaxillary is long and narrow, and oval in section, supports one 

 tooth (the large extremital one), and has two snblongitudinal fossae on the 

 inner side above. Behind these is a fossa divided by inosculating ridges, and 



