252 the merycoidodontid;e 



Matthew (1899, p. 73) considered this species invalid and stated that "there are no distinctions 

 whatsoever from Cyclopidius simus except those due to age of the individual." We know there 

 are certain skull changes between youth and old age, and I believe Matthew's opinion is correct. 

 Schlaikjer considers it a valid species, one of the short, broad, and deep-jawed forms, but it seems 

 to me that these characters are old age and sexual characters combined. 



This species is the genotype of Pithecistes, but since it has been shown that Cope's diagnostic 

 characters for that genus were invalid, it comes into Cyclopidius, as all its distinguishing features are 

 common to the latter genus. 



Cyclopidius decedens (Cope) 1884= ? C. simus Cope 

 PI. XXXVIII, fig. 4 



Original Reference: Synopsis of the species of Oreodontidse. Proc. Amer. Philos. Soc, XXI, p. 558 

 ( Pithecistes decedens ) . 



Type Locality: Smith River Valley, Montana. 



Geologic Horizon: Upper Miocene (Deep River). 



Type: Holotype, Cat. No. 8130 A.M.N. H., part of right maxillary with three teeth. Collected by J. C. 

 Isaac. 



Specific Characters and Discussion: Cope considered the three teeth present in this frag- 

 ment to be P 4 , M 1 , and M 2 ; the last "was not probably entirely protruded." There is also "part of 

 the alveolus of the third true molar." Cope believed that "the animal was fully grown, though 

 young." Matthew ( 1 899, p. 73) also considered these teeth as of the permanent dentition. In view 

 of our recently increased knowledge of the milk dentition of Cyclopidius, I think it is quite evident 

 that the teeth preserved in this fragment are DP 3 " 4 and M 1 . The DP 4 in this genus is decidedly 

 molariform, while DP 3 has a large posterior crescent and a well-developed anterior one. This is 

 the condition seen in the holotype. The permanent P 4 is formed like a half molar, while P 3 has the 

 anterior crescent almost wholly suppressed. So that, even if we argue that Cope's M 1 is really that 

 tooth, we still cannot call the tooth anterior to it P 4 , noting its difference in relative size and so on 

 from the normal proportions in this genus, but must recognize its close similarity to the known DP 3 

 characteristic in this genus. 



So fragmentary a specimen as this is always most unsatisfactory for basing conclusions. How- 

 ever, bearing in mind its youthfulness, it seems to come closer to C. simus than to the other species, 

 although the proportions of M 1 are a little nearer to that of C. densus. The parastyle is somewhat 

 more prominent than normal in C. simus. With wear, this and the mesostyle would probably be 

 reduced in prominence. Matthew considered this a valid species, whereas Loomis and Schlaikjer 

 refer it to C. simus. I believe this reference is justifiable. The infraorbital foramen lies above the 

 anterior part of P 3 . 



Measurements in millimeters 

 DP 3 , anteroposterior 6; transverse 5. 

 DP 4 , anteroposterior 8.7; transverse 7.7. 

 M 1 , anteroposterior 10.7; transverse 9. 



Cyclopidius emydinus Cope 1884 = ? C. simus Cope 



Figs. 180-182 



Original Reference: Synopsis of the species of Oreodontids. Proc. Amer. Philos. Soc, XXI, pp. 553- 

 557, pi. 28, figs. 1-3. 



Type Locality: Smith River Valley, Montana. 



Geologic Horizon: Upper Miocene (Deep River). 



Type: Holotype, Cat. No. 8115 A.M.N.H., nearly complete skull. Collected by J. C. Isaac. 



