486 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



These form two horizontal bony masses of remarkable size, with the ex- 

 terior boMer convex in both the vertical and horizontal planes. The 

 nasal bones are flat and truncate wedge-shaped. The horns are sit- 

 uated above the face in front of the orbit, and are expanded in one 

 plane, so as to be much flattened. Their length is moderate, and their 

 direction outward and forward. There are slight angulations of the 

 frontal and zygomatic margins, which form slight contractions of the 

 zygomatic orbital fossa, one behind the orbit, the other marking the an- 

 terior four- tenths of the zygomatic fossa. The orbits are small and hor- 

 izontally oval, and the temporal fossse contracted. The latter are 

 greatly extended posteriorly, and are bounded by an ear-shaped prolon- 

 gation of the exterior occipital angukir ridge to beyond the line of the 

 foramen magnum. The plane of the vertex and front is wide and unin- 

 terrupted by tuberosities, but forms a gently concave continuum. The 

 dentition is |, f, |-, f . The anterior teeth are all small, the posterior large. 

 There is no internal cingulum on the molars, which are smooth and with 

 low internal cones. 



Measurements. 



M. 



Lengtli of cranium, (33 inches) 0.840 



Width of cranium, (25 inches) .636 



Length of nasal bones to bases of horns .107 



Length of orbit .115 



Width of nasals 152 



Width above orbits .255 



Width, least, between temporal fossiB .170 



Width of mass of zygomatic squamosal .140 



Width between temporal fossse behind .331 



This large quadruped was considerably larger than the S. aoer, Cope; but 

 the horns are shorter, and of an entirely difl!"erent form. Its orbits are 

 remarkably small, and during life the eyes were directed more or less 

 obliquely upward. The broad, flat, wedge-shaped head is not unlike 

 that of suappiug-tortoise (Chelydra) in its physiognomy. 



I append here a description of the mandible, on which the species 

 Symhorodon torvus was established. 1 am not able at present to refer it 

 to its proper cranium, but hope soon to have that opportunity. It nearly 

 resembles that of Symborodon bucco. Dentition; I., (*?) 0; C, 1; P. m., 

 3 ; M., 3 ; the canines slightly separated from each other, but not from 

 the first jjremolarj crowns of the premolars with L-shaped crescents, 

 as in Ehinocertis ; of the molars with completed crescents ; the last molar 

 with third posterior crescent; symphysis mandibuli co-ossified; crowns 

 of canines not projecting, conic. Symphysis oblique ; ramus rather 

 shallow. Last molar with three columnar ribs on the outer side, four on 

 the inner, produced by the continuance inward of the ridges from the 

 anterior and posterior outer cusps. Enamel nearly smooth ; a cingulum 

 round inner basis of crown of canine. 



Measurements. 



M. 



Length of mandibular ramus .• 0.520 



Length of symphysis .144 



Length of series of molars .320 



Length of series of true molars .215 



Length of last molar .083 



Length of penultimate molar .072 



Symborodon ALTIEOSTRIS, Cope, Synop. New Vert. Col., 1873, 12. 

 A large species represented especially by a nearly perfect cranium, 



