COPE.] " PALEONTOLOGY MIOCENE PERIOD. 491 



verse ridges of teeth witli transverse expansions at their inner ex- 

 tremity, being thus T- shaped. 



Measuremeiits. 



M. 



Length from apex of nasals to occipital condyles, (axial, 26.5 inches) 0.664 



Length from occipital condyle to fundus of palate 376 



Length from occipital condyles to end of palatine lamina i^terygoidea 270 



Jjength of four last molars 242 



Length of three last molars 195 



Length of last molar 068 



Width of palate at narial notch 116 



The dental characters of this species ally it to the IS. trigonoceras, but 

 the form as well as the position of the horns is quite different. Instead 

 of being triangular, a section of the base of these is elliptic. • Extremity 

 conical. 



Symborodon htpoceras, Cope ; Miobasileus hypoceras, Cope, MS. 



This species reposes on a fragmentary cranium only, which embraces 

 nasal, maxillary, frontal, malar bones, &c., both zygomata, premolar 

 and parts of molar teeth, &c. These fragments were taken out of the 

 matrix by the writer, and were found in juxtaposition. They represent 

 parts of the same skull, and, as no other was found, in the same bank, 

 are probably without admixture. 



The first characteristic of this species is the elongate form of the face 

 anterior to the orbit as compared with other species. The column which 

 separates the orbit from the infraorbital foramen is flat and has a wide 

 external face, instead of being a cylindric column as in 8. acer, altiros- 

 tris, hiicco, and ophryas. In S. trigon'oceras it is wider, but, instead of 

 being flat, i^resents a strong vertical ridge of the lachrymal bone. The 

 infraorbital canal is hence longer than in those species, the more as it 

 does not communicate with the orbit at as anterior a i)Osition. Between 

 this point and the preorbital border, the orbit is strongly concave. From 

 the infraorbital canal to the narial orifice, the face is flat, and the border 

 of the meatus is thin, somewhat as in HMnocerus, but includes a narrow 

 prolongation of the large sinus common to this genus. The premaxil- 

 lary bone does not appear to enter into it. It is evident from the weak- 

 ness of this support that there could have been no horn of great size 

 or strength above it, and the character of the horn-core preserved is 

 consistent with this view. This consists of the extremital part, thus 

 not exhibiting the basal sinuses. Its section is a compressed oval, nar- 

 rowed in front ; its profile with parallel outlines and a little recurved and 

 not very rugose. Its size as comjiared with the rest of the skull is the 

 smallest in the genus, and not more than half the proportions of the S. 

 altirostris. 



A bone of the upper cranial walls was found in place above the second 

 and third premolars, but presents some puzzling peculiarities of form. 

 It is either the posterior part of the nasals or anterior portion of 

 the frontals, and a short decurved border is either that of the nasal 

 meatus or of the orbit. The left maxillary and lachrymal bones are the 

 ones preserved, and the present bone probably belongs to the same side, 

 which agrees with a mark I placed upon it when I exposed it, indicat- 

 ing the anterior and posterior extremities. There can therefore be little 

 doubt that the element is the frontal. The reason for this investigation 

 is the fact that it sui^ports on its anterior extremity a large os- 

 seous tuberosity, which consists of a mass of bone co-ossified with the 



