NO. 7 MAMMALIA FROM THE ALMY FORMATION — GAZIN II 



sure. About a half centimeter posterolateral and somewhat ventral 

 to the sphenoidal fissure is an aperture which is surely the anterior 

 opening of an alisphenoid canal. The posterior opening is clearly de- 

 fined well forward and ventromedial to the foramen ovale. I am 

 unable to determine the presence or absence of a foramen rotundum, 

 possibly opening into the alisphenoid canal. According to W. K, 

 Gregory (Orders of Mammals, p. 354), a foramen rotundum opened 

 into the alisphenoid canal in Phenacodus; however, Simpson (1933), 

 in describing an endocranial cast of Phenacodtis, shows both first and 

 second branches of the trigeminal nerve as having passed through the 

 sphenoidal fissure. This would seem to preclude the possibility of a 

 distinctly separate foramen rotundum in Phenacodus, which is re- 

 garded as closely related to Ectocion. 



Ventrally, the posterior palatine foramen is about opposite the 

 posterolingual portion of Mi. There is a small, blunt pterygoid proc- 

 ess of the maxilla, and opposing it medially is a somewhat everted 

 lateral portion of the anterior margin of the posterior narial aperture. 

 The nasal cavity is closed below posteriorly to a position about even 

 with the posterior margin of the last molar. The previously mentioned 

 posterior opening of the alisphenoid canal faces more ventrally and 

 well ahead of the foramen ovale, a relative distance nearly as great as 

 in Meniscotherium. The postglenoid foramen is large and placed 

 posteromedial to the postglenoid process, and the space for the audital 

 tube behind the postglenoid process is shallow and broadly open. 



The teeth in U.S.N.M. No. 20736 show the anterior premolars, 

 above and below, to be separated from each other and from the canine 

 by diastemata, the greatest separation being between the first and 

 second premolars, about 4 mm. above and 3 mm. below. The anterior 

 premolars above are simple and 2-rooted, whereas Pi has but one root. 



The essential difference between Ectocion ralstonensis, as exempli- 

 fied by No. 20736, and the Ectocion osborniamim material in the U. S. 

 National Museum from the Gray Bull is to be found, in addition to a 

 slightly smaller size of the teeth, in the less progressive character of 

 the posterior premolars of E. ralstonensis. The tritocone in both P^ 

 and P* is distinctly less developed and less well separated from the 

 primary cusp. This is particularly noticeable in P^. Moreover, the 

 anterointernal cusp or protoconule is less developed. It is not present 

 on P^ and comparatively weak on P* of E. ralstonensis. In E. os- 

 bornianum material at hand, the protoconule is generally prominent 

 and may be thrust to a decidedly anterolingual position in both P^ and 

 P^. There is no tetartocone on the posterior upper premolars of 



