OrnitJiosaurian Genus Ornitliocheirus. 547 



B, C will be found to belong to the distal ends of Groups A, 

 B, C as now classified. That Group A belongs to a genus 

 of the family Oruithodesmidse appears to be certain by a 

 comparison with the humerus of Ornithodesmus latidens, and 

 from Prof. AViiliston^s* description of the distal end of 

 the humerus of Ornithostoma (Pteranodon) we consider the 

 distal ends of Group B to belong to that genus, and there- 

 fore to the edentulous forms of the Cambridge Greensaud. 

 Whether the proximal ends of this group are rightly appor- 

 tioned is a more difficult matter to determine, for the base 

 is all that remains of the deltoid crest, the most characteristic 

 feature. On examination of these specimens it appears that 

 it was oblique to the long axis of the condyle, which, as far as 

 it goes, agrees with Prof. Williston's f description of the crest 

 in Ornithostoma [Pteranodoyi). "This process, the radial or 

 deltoid, has its convex rounded extremity directed obliquely 

 forward and upward and outward/^ yet at the same time it 

 resembles, perliaps in a greater degree, his account of Nycto- 

 sauriis X, " the deltuid, i-adial, or lateral process very large. ^^ 

 "It is directed forward and a little downward.^^ He also 

 says, " The ulnar or median process is very stout." This, 

 together with the fact that the crest is more distal to the 

 condyle in Xyctosaurus, seems to favour a greater affinity to 

 Nyctosaurvs than to the proximal ends in Group B (? Orni- 

 thostoma). Thus, he remarks §, " This crest is further 

 removed from the head of the bone than is the ease in species 

 oi Pteranodon^ Perhaps with the details now given for 

 this group an examination of the American specimens would 

 enable a decision. At anv rate, thev do not belouo; to 

 Groups A or C, and thus in all probability pertain to the 

 edentulous forms. In regard to Group C, typified by the 

 perfect humerus J. a. 6, 30, there is not even a suggestion 

 to be obtained from known facts as to which, if any, of the 

 remaining genera, formed ou the evidence of the premaxillee, 

 it belonefs. 



Radius and Ulna. 

 The specimens on tablet J. a. 9 are the proximal ends of 



* S. W. Williston, " Restoration of Ornithostoma,''^ Kansas Univ. 

 Quart. 1897, p. 45. 



t S. W. Williston, ibid. p. 44. 



X Id. Field Col. Miis. Pub. 78, geo. ser. vol. ii. no. 3, p. 141. 



§ Id. Kansas Univ. Quart, vol. i. 1892-3, p. 6. 



37^ 



