202 



nearly complete, of one individual; by the tooth-bearing bones, palatine arch, 

 muzzle, and sclerotic bones, of a second ; by the tooth-bearing bones, with fin 

 rays, of a third ; and by many cranial .bones, with vertebrae, of a fourth. 

 Three of these individuals had reached a larger size than those of the P. 

 molossus which have come under my observation, 1 and represent the largest 

 species of the Kansas Cretaceous. 



It differs from the P. molossus in the possession of three, and sometimes 

 four, premaxillary teeth. Three is the usual number, but one specimen 

 exhibits a minute fourth, which is present and still larger in another jaw. 

 As P. molossus may in like manner present a variation in the possession of a 

 third minute tooth, it is necessary to note other differences. While the pre- 

 maxillary and anterior portions of the maxillary have the same transverse depth 

 in the specimens of the two species, these elements are notably thinner and 

 lighter in P. ?nolossus, so that the anterior condyle of the maxillary is much 

 narrower and smaller in it than in the P. lestrio. The depth of the maxillary 

 distal to its posterior condyle is also proportionately less in the P. molossus. 

 The measurements of corresponding parts in these species and the P. mudgei 



may be compared as follows : 



Measurements, 



P. inolutsus. P. lestrio. P. mudgci. 



Depth of the premaxillary m .0i)4 ra .094 0'". 070 



Depth of the maxillary behind the posterior condyle . 050 .065 .040 



Width of the anterior condyle of the maxillary .011 .016 ? 



Width of the maxillary behind the posterior condyle .016 .018 .020 



In the specimen first enumerated, the first premaxillary tooth is very 

 large, the two others of moderate size. These are followed by a long rugose 

 diastema before the maxillary teeth begin; these are, one small, five large ; 

 twenty-two small, and eleven or twelve very small. The mandibular teeth 

 are, one very large, one immense, one small, one medium, four small, eight 

 large, and two small — total, eighteen. The teeth are all simply round or oval 

 in section, and the external, probably cementum, layer is smooth. The max- 

 illary hone has two large superior proximal condyles, separated by a space ; 

 the anterior is the narrower, and is directly behind the premaxillary condyle. 

 The anterior margin of the latter bone is very rugose. 



Measurements. 



M. 



Length of the tooth-line of the upper jaw 0.300 



Length i f the tooth-line of the premaxillary 0.058 



Depth of the premaxillary (axial) 0. 095 



1 Bee Proceedings of the Americau Philosophical So iety ion the fishes of the Kansas Cretaceons), 

 January, 1872 



