Bowens DAVIDSON BLACK 
for example, among the ungulates which I have studied in the 
preparation of this paper. 
It is of interest to note in this connection that, in the skulls 
of gyrencephalous mammals of the sub-order Anthropoidea, 
the juga cerebralia and impressiones digitatae are much less 
evident than in the forms about to be described, while in man the 
value of endocranial markings in the determination of convolu- 
tional pattern has recently been seriously questioned (28). 
Various factors must contribute to produce these different 
types of skull growth which are characteristic of different mam- 
malian orders, and it would be irrelevant here to discuss this 
interesting question in any detail. However, as I have else- 
where mentioned, there can be no doubt that among the factors 
‘which combine to cause the condition obtaining in ungulates, 
the following, more especially the second, are most important: 
(a) the habitual position of the head in relation to the action of 
gravity and (b), the early maturation of growth processes in the 
encephalic portion of the skull. 
With regard to my material, | wish to make again the follow- 
ing acknowledgments. 
One-endocranial cast of an adult okapi and one of an adult 
giraffe were obtained in Manchester through the courtesy of 
Prof. G. Elliot Smith, upon whose advice this study was under- 
taken. The second specimen from an adult okapi together with 
that from Samotherium was obtained through the courtesy of 
Dr. Smith Woodward from the Museum of Natural History at 
South Kensington, London. I am indebted also to Prof. Arthur 
Keith for the opportunity of studying the giraffe brains in the 
Museum of the Royal College of Surgeons, and to Dr. C. U. 
Ariéns Kappers for the like privilege of studying the ungulate 
and other material in the collection of the Central Dutch Institute 
for Brain Research in Amsterdam. 
To Prof. Eliot Smith and Dr. Ariéns Kappers, I am fur- 
ther indebted for the helpful criticism of my earlier report. 
