64 NATURE 
[Marcu 18, 1915 

LETTERS TO THE EDITOR. 
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Supposed Horn-Sheaths of an Okapi. 
Mr. R. LypeKker, F.R.S., lately directed attention 
in the columns of Nature to a specimen of the okapi 
sent home by Dr. Christy from the Congo State, 
which was stated to be provided with corneous sheaths 
to its horns, resembling those of an antelope. The 
specimen has been mounted by Mr. Gerrard, of Cam- 
den Town, and is still in his workshop, whilst the 
skull has been purchased by the Royal College of 
Surgeons. I have been given the opportunity of 
examining both the mounted skin and the skull. The 
skull is of an individual of nearly the same size and 
age as that presented to the Natural History Museum 
by the late Captain Boyd Alexander, carefully figured 
under my superintendence with many other skulls of the 
okapi in the atlas of my ‘‘ Monograph of the Okapi,” 
published in 1910 by the trustees of the British 
Museum. With the new skull acquired by the College 
of Surgeons, and apparently belonging to the same 
animal as the skin, is a pair of small ossicones, not 
yet ankylosed to the skull, measuring about 2 in. 
along the longer side from point to base. They are 
of the same shape and little shorter than those of 
Boyd Alexander’s specimen. In neither skull is there 
as yet a tuberculated surface of the frontal bone 
developed for the attachment of the ossicone. In the 
Boyd Alexander specimen each ossicone stood up as 
a projecting cone, and was covered with the hairy 
skin except for a small area at the free end, where 
the hair seems to have been rubbed away, or removed 
in preparing the skin, as may be seen in the mounted 
specimen in the Natural History Museum. In Major 
Powell-Cotton’s specimen, of which both skin and 
skeleton are in the museum, each ossicone is longer, 
slightly compressed from side to side, and claw-like 
in shape, the point curved downward and backward; 
and each ossicone rests on a pitted and tuberculated 
surface of the frontal bone, to which it is closely fitted 
but not yet ankylosed. 
In older specimens, e.g. that in Paris and that in 
Edinburgh, figured in my atlas, there is complete 
ankylosis of the ossicone with the frontal bone, and 
a wide extension of its base. The ossicones of the 
Powell-Cotton specimen are 3% in. in length, and are 
closely covered with hairy skin except, for a length 
of about 4 in., at the tip, which pierces the skin. 
This “tip” of the okapi’s horn, or ossicone (not yet 
developed in the Boyd Alexander specimen), consists, 
as I have described in the Proc. Zool. Soc., 1907, of 
peculiarly dense bony substance, which acquires a 
bright polished surface, and is sharply marked off 
like a nipple, by its raised margin from the rest of 
the bony substance of the ossicone, as seen in all 
adult specimens, of several of which I have published 
drawings. It emerges through the skin as a tooth 
does, when it is said to be ‘‘cut.” 
It is only in their pointed claw-lile 
and the penetration of the skin by the 
tooth-like apex that the okapi’s paired 
differ from the paired ossicones of the 
It is, however, remarkable that the feetal 
giraffe has already before birth two soft hair- 
covered growths corresponding in position and pro- 
portionate size to the paired ossicones of the adult, 
and that the bony ossicones develop in these soft up- 
standing structures soon after birth. The young okapi 
NO. 2368, VOL. 95] 
shape 
hard, 
ossicones 
giraffe. 


has no such tegumentary growths, and the ossicone 
makes its appearance when the animal is nearly full 
grown or completely so as a free button-like ossifica- 
tion lying beneath the integument, which is pushed 
upwards by it as it grows. ‘The dense emerging point 
of the okapi’s ossicone forms for the animal a very 
efficient weapon. The giraffe’s ossicone never pene- 
trates the skin, but its apex-is broad and flat and 
clothed with a tuft of long black hair. The axis of 
the okapi’s ossicone is not at right angles to the 
horizontal plane of the skull, but is directed back- 
wards so as to form an angle of 45° with that plane. 
Mr. Gerrard tells me that wrapped in the bundle 
with the skin of Dr. Christy’s specimen as received 
by him were two hollow, bluntly ending corneous 
horn-sheaths of about 23 in. in length, which he was 
led to suppose belonged to sthe animal. He has 
mounted these two hollow horn-sheaths on the top of 
the animal’s head over the holes in the skin made 
in originally clearing it from the ossicones (when the 
skin was prepared in Africa) which have gone with 
the skull to the College of Surgeons. These hollow 
horns do not fit well to the cut skin, and there is 
no intrinsic evidence forthcoming to justify the asso- 
ciation of them with the okapi’s skin. They have 
the appearance of young horn-sheaths of some species 
of antelope, and show a few ring-like markings on 
the surface. They taper only slightly from base to 
tip, and the tips are rounded and blunt. It is, I 
admit, conceivable that in the early period of its 
growth before the completion of its ivory-like point 
and the cutting by it of the skin, the ossicone of 
the young okapi might develop a temporary corneous 
sheath to be shed during further growth and re- 
placed by hairy skin. The prongbucl sheds its horn- 
sheath yearly, and very young cavicorns have been 
observed to shed a first sheath before acquiring a 
permanent one. Hence it is not impossible that a 
temporary corneous sheath should develop from the 
skin covering the young ossicone of the okapi. 
The real question in such a matter is what is the 
evidence in favour of the unlikely but possible occur- 
rence? The fact that between fifty and a hundred 
skins and skulls of the okapi have reached Europe 
in the last twelve years, and that no such horn- 
sheaths have hitherto been seen or heard of, is im- 
portant. It is also important to bear in mind that 
it is quite certain that when once the okapi is full 
grown and its ossicone is ankylosed to the skull, it is 
covered by hairy skin like that covering the skull, 
from which its naked ivory-like point emerges. 
The evidence is as follows. Mr. Gerrard tells me 
that he was led to believe that the small horny sheaths 
sent with the skin of the okapi actually belonged to 
the specimen by the fact that when removed from 
the parcel a label was found tied to them on which 
was written, ‘‘ Horns of the Okapi.’’ This would cer- 
tainly seem to justify Mr. Gerrard in mounting them 
on the head, as he did. 
He has, however, since I saw the specimen, sent 
me a note just received by him from Dr. Christy. 
This is headed, ‘‘Details of Okapis obtained with 
numbers of cases and dates of dispatch.”’ It is signed 
by Dr. Christy, and dated Khartoum, February 10, 
1915. It appears that Dr. Christy has been employed 
on a mission in the Congo State during 1913-14 by 
the Belgian Government, and that he had forwarded 
during those years specimens collected by him to 
Brussels to be sent on to Mr. Gerrard, acting as his 
agent, in London. Seven specimens of okapi are 
mentioned in the list before me, and the date of shoot- 
ing and the name of the ship and route by which they 
were dispatched are given. Some were sent off in 
1913, others in 1914. Mr. Gerrard tells me that only 
one—the one he has mounted—has reached him in 
