286 



DE. E, EAY LANKESTER ON OK API A. 



There is good ground for connecting the presence of the defioction of tlie cranial 

 cavity, above noted, with the mechanical conditions arising from the use of horns 

 having the position and direction of those found in Bovidse and the Giraffe. Even in 

 the hornless females of certain Antelopes the deflection is maintained (text-fig. 7, 

 p. 287). The absence or small size of the deflection is almost certainly to be regarded 

 within the group Pecora as a primitive character, and in the horizontality of the skull 

 or tendency to coincidence of the basicranial and basifacial axis-planes the Okapi bears 



Vertical longitudinal section of the skull of a Giraffe, to show the air-sinuses and the relatively low angle 

 formed by the basicranial axis (cm.) and the palatine horizontal {p.h.). 



occ, occipital crest ; 2^-oss., parietal ossicusp ; g.t.m.. Giraffe's median tumescence, upon which the median 



osseous cap develops. 



Te.xt-fiR. fi. 



occ 



/J./S-. 



Vertical longitudinal section of the skull of a female Elk (Alces), to show the low angle formed by the 

 basicranial axis (cff.) and the palatine horizontal (pJi.). 

 occ., occipital crest. 



evidence of (1) being relatively primitive, (2) not having had horn-bearing forebears, 

 (3) of being remote from the Cavicorn stock. 



A further character, at once obvious on examination of the Okapi's skull, is the 

 absence of the lacrymal fossa — present in many Antelopes and all the Cervidse, but absent 

 in Girafies. This, however, is not a diagnostic character, since the lacrymal fossa is 

 not present in all Antelopes. Equally inconclusive is the existence of the "prselacrymal 

 vacuity " (PI. XXXII. fig. 12, c), which is well marked in the Okapi's skull and in all 



