556 



PROCEEDINGS OF THE XATIOXAL MUSEUM. 



vol. 48. 



Measurements of skulls of Equus quagga chapmani in millimeters, with indices. 



Specimens. gjg" 



Vertex 

 length. 



Frontal 

 width. 



Co- 



phalic 

 index. 



P^-, Cranio- 



Facial 

 length. 



Facio- 

 cephalic 

 index. 



For. 

 mag. to 

 vomer. 



Vomer 



to 

 palate. 



5239, Salensky 



5240, Salenskv 



448 

 452 



501 

 513 



202 

 1S4 



45.1 



40.7 



165 



159 



36.8 

 35.2 



344 

 356 



76.8 

 78.7 



106 

 106 



109 



112 



Averages 



450 



507 



193 



42.9 



162 



38.0 



350 



77.7 



106 



111 



In the case of Salensky's specimen (Xo. 5239) of Chapman's 

 zebra one might reasonably suspect some error. If the measurements 

 and indices are compared with those of Equus hemionus, the two 

 sets will be found to be remarkably similar. 



Measurements of skulls of Equus q. obhmi and E. q. eunninghami in 



millimeters, with indices. 



Specimens in U. S. 'Basilar 

 National Museum, length. 



Vertex 

 length. 



Frontal 

 width. 



uhalic Cranial 



ESS: le ^ th - 



Cranio- 



cephalic 



index. 



F • , Facio- 



For. 

 mag. to 

 vomer. 



Vomer 



to 

 palate. 



E.q.bolimi, 181825... 



E. q. eunninghami, 



1S2156 



488 

 435 



sea 



500 



192 

 188 



39.3 194 

 43.0 166 



39.7 

 38.2 



370 

 335 



77.9 

 77.0 



127 

 109 



114 



102 









If now there are determined the averages of the measurements and 

 indices of all the specimens of Grant's. Crawshay's. Chapman's, 

 Boehm's. and Cunningham's zebras, leaving out only the suspected 

 specimen of Chapman's mentioned above, there are obtained the 

 following : 



Combined measurements and indices of subspecies of Equus quagga in 



millimeters. 





Basilar 

 length. 



Vertex 

 length. 



Frontal 

 width. 



Cephalic 

 index. 



Cranial 

 length. 



Cranio- 

 cephalic 

 index. 



Facial 

 length. 



Facio- 

 cephalic 

 index. 



Averages 



446 



514 



186 



41.6 



172 



38.3 



347 



77.5 







By considering the difference between the greatest and the least 

 values shown in each of the respective columns devoted to the 

 various subspecies and bringing them into comparison with the cor- 

 responding average it will be seen that the basilar length varies by 

 an amount less than 14 per cent of the average; the frontal width 

 less than 10 per cent; the facial length about 12 per cent. The 

 cephalic index varies to the extent of 12.5 per cent of the mean. The 

 variation of the cranio-cephalic index is greater, about 21.5 per cent. 

 Within the subspecies granti it varies to the extent of 15 per cent. 

 It seems possible that the wide range here may be due to the greater 

 or less development of the occipital crest : not improbably the brain 

 is considerably larger in some individuals than in others. 



