82 0. C. Marsh — Horned Artiodactyle from the Miocene 



Between the orbits, the frontals are depressed, and marked 

 by two deep grooves leading backward to the supra-orbital 

 foramina. Behind these, halfway to the horn-cores, is a 

 median prominence resembling in shape the corresponding 

 elevation on the skull of the male giraffe. The brain cavity 

 is unusually large for a Miocene mammal. The occiput is 

 very narrow, indicating a small cerebellum, and the occipital 

 crest is weak. The occipital surface slopes backward. 



The facial region of the skull is narrow and elongate. On 

 the outer surface, of the maxillary, just above the antorbital 

 foramen, there is a deep depression, which probably contained 

 a gland. The usual ruminant fossa in front of the orbit 

 appears to be wanting. The orbit is large, and completely 

 closed behind by a strong bar of bone. 



The dentition preserved is selenodont and brachyodont, with 

 only three premolars and three molars. The first premolar is 

 much compressed transversely, and has but a slight inner lobe. 

 The second premolar is triangular in outline, the inner lobe 

 being much more developed. The last premolar has this lobe 

 expanded into a strong cusp, and the crown thus becomes broader 

 than long. The true molars have two inner cusps, each with a 

 basal ridge. The outer crescents have a median vertical ridge. 

 The enamel of the molar series is more or less rugose. There 

 was a wide diastema in front of the premolars. 



The posterior nares are situated far forward, the anterior 

 border being opposite to the posterior cusp of the second true 

 molar. The glenoid facet is large and convex, but the post- 

 glenoid process is quite small The paroccipital processes were 

 well developed, but there were apparently no auditory bullae. 



This skull when entire was about eight inches (200 mm ) in 

 length. The distance between the orbits across the frontals is 

 about three inches (75 mm ), and the distance between the sum- 

 mits of the horn-cores, about one and one-quarter inches 

 (32 mm ). The extent of the premolar and molar series is three 

 and one-eighth inches (80 mm ), and the width of the palate 

 between the true molars is one and one-quarter inches (32 mm ). 



As the animal represented by this skull is very distinct from 

 any hitherto described, the genus may be named Protoceras, 

 in allusion to the early appearance of horns in this group. 

 The species may be termed Protoceras celer. The characters 

 now known suggest affinities with the giraffes, but indicate a 

 distinct family, which may be called the Protoceratidce. 



The geological horizon is in the upper part of the Oreodon 

 beds of the Miocene. For securing this important specimen, 

 the writer is indebted to his able assistant, Mr. J. B. Hatcher, 

 whose many discoveries in the West are well known. 



New Haven, Conn., December 17, 1890. 



