402 R. Owen — Existmce or not of Horns in the Dinocerata. 



afterwards coalesces with a cranial bone, or that it grows, as a 

 process, from a cranial bone. 



The giraffe yields an instance of the " autogenous " horn, and 

 its skull, in either the recent or fossil state, shows the basal sutures. 

 In other species the horns or horn-cores are " exogenous ;" and 

 such, in the absence of the sutural evidence, are the parts called 

 " horn-cores " in the Dinocerata. 



But before elevations or processes of cranial bones can be pro- 

 nounced to be " horn-cores," the evidence of the horns they sup- 

 ported should be forthcoming. Paleontology, it is true, infers the 

 existence of horns supported on bony bases, or " horn-cores," in ex- 

 tinct species in which such horns have perished, hos antiquics^ 

 Bison prisms, Sivathervwn, Bramatherium, are rightly referred 

 to the " hollow-horned " group, and the two latter may seem more 

 germain to the present question, seeing that the " horn-cores " are 

 in two pairs. Such conclusion is based on the presence of foramina 

 and ramified grooves upon the surface of the " cores," which are 

 known to be the effects of the penetration and pressure of blood- 

 vessels supplying the growth and renovation of the horny sheaths 

 of such bony processes. The same evidence reveals the true na. 

 ture of the horn-cores, which may be covered with skin instead of 

 horn, such as are the horns of deer, from which when complete the 

 skin is shed. 



In the absence of such evidence the paleontologist infers that 

 smooth un furrowed protuberances or processes of cranial bones 

 were covered, like the rest of the outer surface of the bones devel- 

 oping them, with persistent periosteum and skin, in the existing 

 animal. He refrains from calling them " horn-cores," and from 

 defining the extinct species manifesting them, as " horned," " four- 

 homed," or " six-horned," Bicerata, Tetracerata, Hexacerata ; or, 

 as in the case of the hornless herbivores of the Wyoming Eocene, 

 Binocerata : because such tei-ms imply the possession by those ex- 

 tinct quadrupeds of weapons of which there has not, at present, 

 been given any evidence. 



Professor Marsh, indeed, candidly admits in regard to the pro- 

 tuberances which suggested the generic name Binoceras, that they 

 " may possibly have been covered with thick skm and not with 

 true horn."f But we have no evidence of the integument having 

 been thicker, or other on the protuberances than on the cranial 

 bones developing them. 



It may be noted that the hornless exceptions in the group of 

 existing herbivorous quadrupeds with true horn-cores and horns, 

 the hornless Moschidce, e. g., are furnished with other weapons of 

 defense, a pair, namely, of long, edged, and sharp-pointed canines 

 descending from the upper jaw. 



The hornless Binoceras was similarly armed, and Professor 



Marsh believes he has evidence of a sexual difference of size in 



those dental weapons, which would yield another analogy to the 



existing Musk-deer. But the dental and osteal characters of the 



tLoc.cit.,p.l64. 



