10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



cast are concealed by the squamosal or are damaged so that its outline 

 can only be approximated ; nevertheless, its form was evidently very 

 close to that of Smilodectes. Its length seems very nearly the same 

 but its width may be a little less, although there is some distortion 

 evident in the N otharctus cast. It cannot, however, be regarded as 

 narrow (see Gregory, 1920, p. 168) in comparison with Lemur. The 

 extent of the neopallium was presumably much like that in Smilo- 

 dectes. Representation of the anterior part of the vermis cerebelli is in 

 view and was noted by Gregory to be exposed as in Lemur. It is essen- 

 tially like that in Smilodectes. While no mention is made by Gregory 

 of the cerebellar hemispheres, representation of that on the right is 

 faintly discernible, although the one on the left is completely 

 concealed. 



The exposed portion of the Notharctus tenebrosus endocast is about 

 30 mm. long by 25 mm. wide. It is estimated, however, that the total 

 length over the cerebral and cerebellar lobes may have been between 

 32.5 and 35 mm., and the width over the temporal lobes between 27.5 

 and 30 mm. 



Comparison of the Smilodectes endocranial cast with endocranial 

 detail reported by Gregory for the fragmentary skull of Notharctus 

 venticolus (A.M. No. 14656) could not be made inasmuch as this 

 Wasatchian skull has since been restored for exhibition. The "N. 

 matthew" specimen (A.M. No. 13030) cited by Gregory includes a 

 petrosal which contributed to his study. This, however, represents 

 Smilodectes and closely resembles the petrosal belonging to U.S. 

 National Museum No. 23276. 



Adapts. — A comparison of the Smilodectes endocast with that 

 described for later Eocene Adapts parisiensis was greatly facilitated 

 by Neumayer's excellent appearing figures (1906, pi. 5), reproduced 

 in Gregory's monograph on Notharctus (1920, fig. 63), and by the 

 photograph provided by Hofer (1962). From these it is seen that 

 the details of the short and relatively very broad cranial cavity of 

 Smilodectes are very unlike those of the Adapts specimen, further 

 emphasizing the distinctness of the Notharctidae. However, this is 

 not in agreement with Gregory's unaccountable statement that the 

 endocast of N otharctus "is obviously of the same general type, save 

 that in Adapis the temporal lobes are more expanded transversely . . ." 

 The cerebral hemispheres of Smilodectes, as well as being relatively 

 shorter and broader than in Adapis, show evidence of incipient sulci 

 presumed to be lateral and suprasylvian. These are not indicated in 

 Neumayer's figures for Adapis, but of more significance, the anterior 



