GEOLOGICAL SUEVEY OF THE TEREITOKIES. 329 



Challc of Kansas. 



Clidastes 3 



Edestosaurus 4 



Holcodus - '1 



Liodon 6 



17 



We liave additional species from — 



JSTortli Carolina, (Mosasaurus) 1 



Mississippi, (Platecarpus) 1 



Nebraska, (Mosasaurus) 1 



Making, with the others from — 



New Jersey 15 



Alabama 7 



Kansas ^ 17 



A total of . - 42 



Of these I am not acquainted with any which extends its range into 

 any two of the areas above named, while some of these districts 

 possess peculiar genera. It is, nevertheless, premature to draw any 

 conclusions as to geograpbical range, as most of the species are 

 known from but few specimens as yet. 



The present investigations have added some points of importance to 

 the history of the structure of the order. 



First, as to the pterygoid bones. It appears that these elements are 

 thin plates, having a free laminar termination, and are entirely tooth- 

 less. They articulate with tbe palatines by a process which fits the pos- 

 terior emargination of the latter. In the Edestosaurus tortor they are 

 about half the length of the palatines. They present no indications of 

 ectopterygoid. The bones named by authors pterygoids, in imitation 

 of Cuvier, are elongate palatines, and the external process extending 

 to the maxillary is that seen in Varani, serpents, &c., and is at no time 

 distinct from the palatines. 



Secondly, as to the parieto-squamosal arch, which is well developed. 

 It is j)reserved in Holcodus ictericus and Liodon curtirostris in its parietal 

 part, and H. coryphaeus in the squamosal part. It was quite strong in the 

 species named. 



Thirdly, as to the pelvis. This part, which has been observed by Marsh 

 in Edestosaurus dispar, is unusually perfect in Liodon dyspelor. The 

 pubes are the only elements united below, forming a weak support to 

 the abdomen. The ilia are slender, not united with the vertebral pro- 

 cesses above, or without indications of such contact. The ischia are 

 the most slender and directed backward. The peculiarities of the i)elvis 

 add to the broad distinction between this order and tbe Lacertilia. 



Fourthly, in the hind limb. The femur of L. crassartus has been 

 described by the writer, and Professor Marsh asserts its existence in 

 Liodon, Clidastes, and Edestosaurus. The present collection exhibits both 

 femur, tibia and fibula of L. dyspelor, and these elements are now first 

 described. The hrst mentioned is not larger, sometimes smaller, than 

 the humerus, and has a prominent trochanter, nearly connected with 

 the head. The shaft is not curved, and the distal end is expanded. 



