Professor 0. C. Marsh— The Skull of Protoceras. 435 



a true proboscis. The only existing ruminant thus equipped, known 

 to the writer, is the rare Saiga antelope (Saiga Tartarica, Gray) 

 from the steppes of Siberia. A comparison of a Protoceras skull 

 with that of the Saiga antelope plainly indicates, in the nasal region, 

 an identity of function doubtless accompanied by a similar nasal 

 appendage, and it is of interest to find such evidence of this feature 

 in a representative from the Miocene of North America. 



The general form of the male skull of Protoceras is long and 

 narrow, with the facial portion much produced. The prominent 

 horn-cores, however, serve to obscure its real shape, which is more 

 apparent in the female skull. Seen from the side, as in Plate XIX, 

 it appears unusually low, with the orbit well behind. Its greatest 

 width is in the posterior region. 



The premaxillaries are small and edentulous. Their anterior 

 extremities are depressed, and more or less expanded transvei'sely, 

 as in typical ruminants. The outer suture between the premaxillary 

 and maxillary is short, and persistent even in adults. Seen from 

 below, the premaxillaries form together the palatal surface in front 

 of the maxillaries, each sending backward a narrow process which 

 is inserted between the divergent maxillary plates. The anterior 

 palatine, or incisive, foramina are situated on the sutures separating 

 the two bones. 



The maxillary bones are greatly developed, being much the 

 largest elements of the skull, as shown in Plate XTX. The anterior 

 extremity supports the large descending canine tusk, and is hollowed 

 out to contain its base. The high anterior horn-cores are formed 

 entirely of the maxillary bones, which are greatly strengthened to 

 support them. These horn-cores are more or less recurved, and in 

 the type-species their summits are triangular in outline. In another 

 species, Protoceras nasutns, the summits of the maxillary horn-cores 

 are oval in section. Another characteristic feature of the genus 

 Protoceras, which is seen in both sexes, is a strong lateral ridge 

 extending nearly horizontally across the outer face of the maxillary 

 bone, and continuing backward to the orbit. In the male skull 

 here described, this ridge begins near the base of the maxillary 

 horn-core, and, expanding into a prominent tubercle, just above the 

 antorbital foramen, continues backward by an upward curve, and 

 passes into the ridge of the malar bone extending beneath the orbit. 

 In both sexes, the anterior portion of this lateral ridge, with its 

 characteristic tubercle, forms the lower border of a deep, well-marked 

 depression, which probably contained a gland. In Plate XIX this 

 cavity is well shown behind the maxillary horn-cores, just below the 

 point where the superior border of the skull is lowest. 



The nasal bones join the maxillaries above, and complete the 

 posterior border of the large narial opening. They are of moderate 

 length on the median line, and their free anterior extremities are 

 quite short. These bones are much expanded transversely, and at 

 their widest part articulate with the lachrymals. All the sutures 

 surrounding the nasals are distinct, and this is true also of their 

 median suture. Their upper surface is convex, both transversely 



