276 DAVIDSON BLACK 



among the Anthropoidea than in other mammahan orders and 

 greatest in man in whom postnatal brain growth and differenti- 

 ation is continued for many years. 



I have elsewhere observed (1) that one of the most important 

 conditions contributing to the endocranial reproduction of cere- 

 bral pattern lies in the early maturation of growth processes in 

 the encephalic portion of the skull. Since this condition is less 

 nearly fulfilled in man than in any other mammalian form, it is 

 to be expected that the human juga cerebralia and impressiones 

 digitatae will be correspondingly poorly developed. Conversely 

 with but few exceptions one may look for close endocranial and 

 encephalic correspondence in gyrencephalous mammalian types 

 below the anthropoidean scale, and even within the latter group 

 in the less generalized primitive extinct forms. 



DESCRIPTION OF SPECIMENS 

 Specimen I (figures 1 to 4 and 27 to 30) 



The cerebral portion only of the endocranial cast is represented, 

 so that nothing can be learned of the structures which occupied 

 the olfactory skull fossae nor of those situated below the plane 

 of the tentorium in this specimen. 



The transverse diameter of the cast is greatest in its posterior 

 third, dorsal to the groove corresponding to the rhinal fissure, 

 where it measures 4.3 cm. The maxunum transverse diameter 

 between the eminences corresponding to the pyriform lobes is 

 4.1 cm. From the frontal to the occipital pole of the cast the 

 maximum length is 4.1 cm. and the maximum height is 3.0 cm. 

 The volume of the cast is 28 cc.^ 



Basis cerebri. (Fig. 4.) On the basal surface the relation of 

 the diverging medial and lateral olfactory tracts to the prominent 

 protuberance of the bulbus olfactorius and to the pyriform lobe, 

 is- clearly indicated on both right and left sides of the cast.^ In 



2 In this and succeeding specimens the volume was determined by the water 

 displacement method so these figures can only be considered as approximate. 

 The linear measurements are all taken to the nearest tenth. 



* For convenience throughout this description many of the surface markings 

 which of course are all the result of moulding of the natural cast by endocranial 

 structures, will be referred to as parts of the central nervous system. 



