4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



sinus, which is much less distinct forward along the midline. Poste- 

 riorly it terminates in a small, prominent knob, evidently homologous 

 with the torcular Herophili in man, but lodged in the parietal rather 

 than in the occipital portion of the skull. From here the lateral sinuses 

 are not represented on the cast until their emergence is noted near the 

 anterolateral margin of the lateral cerebellar lobes. 



The surface of the cerebral portion of the cast, owing to the nature 

 of the matrix, shows remarkably fine though incomplete detail of the 

 network of meningeal blood vessels in the dura mater. The surface 

 of the neopallium, as interpreted from the surface of the cast, which 

 strictly speaking represents only the surface of the dura mater with 

 its vascular detail, was evidently nearly, but not quite, lissencephalic. 

 A very shallow, broadly concave depression extends along both sides 

 of the midline in a slightly arcuate, medially convex, path from about 

 even with the frontoparietal suture to approximately the posterior 

 lobes. At the anterior extremity the depression becomes appreci- 

 ably deeper where it is joined by another feeble depression extending 

 posterolateral^, approximately paralleling the anterolateral margin of 

 the hemispheres. It is observed moreover that the two sides are not 

 quite symmetrical with respect to these features, as the longitudinal 

 depression is a little better denned but not so elongate on the left. 

 Also, the anterolateral depression is better denned on the left, ap- 

 pearing somewhat discontinuous on the right. Presumably these are 

 representations of incipient sulci forming in the neopallium, possibly 

 in response to stresses set up in the transversely already widely ex- 

 panded mantle in accordance with Le Gros Clark's (1945a) concept, 

 although this would be disputed in favor of a more intrinsic explana- 

 tion by Connolly (1950). The absence of transverse depressions 

 would seem in keeping with the small freedom of expansion still 

 remaining at the anterior and posterior poles, in the phylogenetic 

 development. 



Speculation as to the possible homologies of these shallow depres- 

 sions in terms applicable to the sulci of the neopallium is perhaps 

 unwarranted ; nevertheless, one is tempted to suggest possible correla- 

 tions. There seems some likelihood that the anteroposterior depres- 

 sion near the midline is related to the sulcus lateralis or the intra- 

 parietal, as this is described as one of the more stable and earlier to 

 appear in the various Mammalia. By itself the more anterolateral 

 depression suggests the coronal or rectus, as it appears along this 

 margin in Lemur, but its relation to the presumed sulcus lateralis 

 would appear anomalous since they converge forward rather than 



