2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



The natural cast was developed through flaking off of pieces of 

 bone by careful use of needle and dental tools. This was made pos- 

 sible by the fineness and induration of the internal matrix which 

 revealed a cleavage at contact with the endocranial surface. While 

 essentially all of the dorsal portion and left side of the cast was 

 exposed in this way, the bone on the right side in the ear region was 

 preserved in place for reference purposes. For the latter use, more- 

 over, it was found possible to reassemble portions of the parietal and 

 supraoccipital material removed. Fortunately, an appreciable part of 

 the left temporal area was removed intact without damage to the cast. 

 The only portion of the cast missing is the anterior segment represent- 

 ing the olfactory lobes, presumably included with the unrecovered 

 rostral portion, so that the cast is complete only to the olfactory roots 

 or peduncles. 



Information on endocranial casts of fossil primates from the Ter- 

 tiary of North America is extremely meager. Cope early (1884, 

 p. 246) reported exposure of the natural cast of the left cerebral 

 hemisphere in the skull of Tetonius homunculus, stating that he was 

 leaving further examination of it for a future time. So far as I am 

 aware, however, he made no further study of it, although in the fol- 

 lowing year (1885) he noted a resemblance in the size of the brain 

 and hemispheres to those of Tarsius. In 1959 Le Gros Clark also 

 commented on the TarshtsAike appearence of the cast. A partially 

 exposed natural cast of Notharctus "tyrannus," together with certain 

 details of brain cavity in other notharctid specimens, was reported 

 by Gregory (1920). His description of this material, including com- 

 parison with Adapis parisiensis, is rather brief and only the Adapts 

 endocranial cast is figured (after Neumayer). Most recently, at the 

 1964 annual meeting of the Society of Vertebrate Paleontology, Dr. 

 John A. Wilson reported on the discovery of a remarkably good 

 primate skull from the early Tertiary of Texas, which has exposed 

 part of the dorsal surface of the endocranial cast. Further informa- 

 tion on this interesting specimen is anxiously awaited. 



The pencil-shaded drawings of the Smilodectes gracilis endocranial 

 casts included with this report were prepared by Lawrence B. Isham, 

 scientific illustrator for the Department of Paleobiology of the U. S. 

 National Museum. I am indebted to Dr. Tilly Edinger for sugges- 

 tions and information on undescribed related materials, and to Dr. 

 Malcolm C. McKenna for having the plaster cap removed from the 

 Notharctus endocranial cast. 



