256 



THE MERYCOIDODONTID/E 



Genus CYCLOPIDIUS Cope 1878 

 Subgenus Chelonocephalus Thorpe 1921 



Table 13 



Original Reference: Leptauchenia Leidy and Cyclofldius (Pithecistes) Cope. Amer. Jour. Sci. (5), 

 I, pp. 415-418, figs. 4-6. 



Genotype and only Species: Chelonocephalus schucherti Thorpe. 

 Genoholotype: Cat. No. 10123 Y.P.M., skull. 



Distinguishing Characters: See under Specific Characters. 



Discussion: This middle Miocene representative of the Leptauchenia-Cyclopidius stock has 

 the family characters to an exaggerated degree and has reduced its size materially over its contempo- 

 raries in Montana. I do not feel that it is entitled to generic rank, though from the nature of the 

 differences it is possibly entitled to be regarded as a subgenus. Loomis and Schlaikjer consider it 

 within the genus Cyclopidius, and I realize fully all of the similarities to Cyclofldius. But while 

 the species undoubtedly belongs in that family, several characters have advanced considerably 

 beyond the normal Cyclopidius form, such as: the extreme foreshortening of the basicranial region; 

 the extreme brachycephaly; the deeper intrusion of the vacuities into the frontals, lacrimals, and 

 maxillaries; the greater shortening of the muzzle; and the proportionally larger bulls. 



Etymology: Chelonocephalus (turtle + head). 



/Ot 23, TYPE 

 Y P. M. 



Fig. 183. — Cyclopidius {Chelonocephalus) schucherti Thorpe. Skull. 



(After Thorpe, 1921.) 



HT. Cat. No. 10123 Y.P.M. Nat. size. 



Chelonocephalus schucherti Thorpe 1921 

 Figs. 183-185 



Original Reference: Leptauchenia Leidy and Cyclofldius (Pithecistes) Cope. Amer. Jour. Sci. (5), 

 I, pp. 415-418, figs. 4-6. 



Type Locality: Near Hermosa, South Dakota. 



Geologic Horizon: Middle Miocene (Sheep Creek). 



Type: Holotype, Cat. No. 10123 Y.P.M. , well-preserved adult skull, lacking occipital condyles and incisive 

 border. Collected by H. F. Wells, 1894. Specific name was given in honor of Professor Charles Schuchert. 



Specific Characters: The skull is smaller than in the species of Cyclopidius s. sir., with the 

 exception of C. califomicus, and is roughly circular in outline. The relatively great bizygomatic 

 diameter is very marked, with the greatest expansion just ahead of the glenoid surface. The malar 



