254 THE MERYCOIDODONTID^: 



Loomis (1925A, p. 248) grouped all of the Deep River forms into two types, the short-faced, 

 headed by C. simus, and the long-faced, with C. emydinus as the example. In the known skull 

 types from which we can get dimensions, the indices of length of face in front of the orbits to the 

 total skull length work out as follows: C. emydinus, 0.258, and C. simus, 0.322 (both Deep River 

 forms, and varying very slightly in both dimensions — probably more complete skulls would show a 

 closer agreement in indices); C. densus, 0.284, and C. lullianus, 0.391 (both Goshen Hole speci- 

 mens). These indices show that all the Cyclopidius species have a characteristically short muzzle, 

 and if any one is to be designated as long-muzzled, it should be C. lullianus. 



Fig. 182. — Cyclopidius emydinus Cope. Inferior view of skull. HT. Cat. No. 8115 A.M.N.H. 3/5 nat. size. 



(After Cope, 1888.) 



The proportion of molar to premolar length shows an index of above 0.70 for the Deep River 

 forms and below 0.70 for the Wyoming ones, as follows: C. emydinus, 0.74, C. simus, 0.75, and 

 C. incisivus, 0.78 (all Deep River); C. densus, 0.60, and C. lullianus, 0.69. 



Cyclopidius feliceps (Cope) 1878 = C. simus Cope 



PI. XXXVIII, figs. 9-10 



Original Reference: Descriptions of new Vertebrata from the Upper Tertiary formations of the West. 

 Proc. Amer. Philos. Soc, XVII, pp. 220-221 (Brachymeryx feliceps). 

 Type Locality: Smith River Valley, Montana. 

 Geologic Horizon: Upper Miocene (Deep River). 

 Type: Holotype, Cat. No. 8126 A.M.N.H., palate with deciduous premolars and with M 3 not erupted. 



Discussion: This is a young C. simus and was recognized as such by Cope in 1884. He mis- 

 took the milk for the permanent dentition, and was thus led into an error in erecting a new genus, 

 Brachymeryx, and a new species for this palate. 



Measurements may be taken from the figures. 



Cyclopidius heterodon Cope 1878 = ? C. simus Cope 



PL XXXVIII, fig. 5 



Original Reference: Descriptions of new Vertebrata from the Upper Tertiary formations of the West. 

 Proc. Amer. Philos. Soc, XVII, p. 222. 



Type Locality: Smith River Valley, Montana. 

 Geologic Horizon: Upper Miocene (Deep River). 



Type: Holotype, Cat. No. 8131 A.M.N.H., part of right maxillary with P 4 and M 1 . Collected by J. 

 C. Isaac. 



