192 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Foi.VI. 



M. 



Length, of first true molar 0044 



Width of first true molar in front 0028 



Elevation of first true molar in front 0025 



Depth of ramus at second premolar 0064 



Depth of ramus at tubercular molar 0070 



This species is dedicated to my friend Prof. W. Boyd Dawkins, the 

 distinguished geologist and paleontologist, of Manchester, England. 



27. Stypolophus strenuus Cope. 



Portions of two individuals, with lower jaws, etc. 



28. lOTOPS Bicuspis Cope. 



St!fpolo2)hus dicuspis Co]5e, American Naturalist, 1880, Oct. ]i. 746. 



The genus Ictops was determined by Leidy from a species, the I. dako- 

 tensis Leidy, from the White Eiver formation. The animal now men- 

 tioned is identical with it in generic characters, so far as they are ascer- 

 tained. The I. dalcotensis is established on a specimen which does not 

 contain all the teeth, but the parts preserved indicate that those which 

 are wanting are hke the corresponding parts of Leptictis Leidy and Bfeso- 

 dectes Cope, with which the present species also agrees. It is unexpected 

 to identify a genus found on the White Eiver horizon with one from the 

 Wasatch. Ictops agrees very closely with Didelphys. The fourth supe- 

 rior premolar has an internal cusp, which is wanting in Didelphys, and 

 the inferior border of the mandible is not inflected. There are also but 

 three superior incisors on each side. Under these circumstances I pre- 

 fer to refer this genus to the Bunotlieria rather than to the Marsupialia,. 

 but whether its proper place is in the Creodont or Insectivorous subdi- 

 visions I cannot yet determine. 



Char, specif. — Smaller than the Stypolophus minor Filh., and not very 

 different in dimensions from the Ictops dalcotensis Leidy. It is repre- 

 sented by a nearly complete skull, with entire dentition of both jaws. 

 Premaxillary bones rather elongate ; general form of skull that of a civet. 

 Crowns of second and third superior premolars compressed, with a promi- 

 nent cusp behind the principal one. First and second true molars with 

 two distinct external cusps and a strong exterual basal cingulum. Infe- 

 rior first premolar one-rooted, third with a posterior heel, and fourth 

 with strong anterior and especially posterior heels. Heels of true mo- 

 lars well developed (last broken). Length of superior dental series to I. 

 1, .031; length of molar series, .020; length of true molars, .006; depth of 

 mandible at second true molar, .007 ; depth at canine, .0035. The double- 

 lobed third premolar and the smaller size distinguish this species from 

 the Stypolophi. 



29. Ictops didelphoides sp. nov. 



Established on a left mandibular ramus, which supports the last three 

 molars. This demonstrates the former existence of a species of larger 



