1836.] a new Fossil Genus of the Sivdlik range. 41 



Outer Inner 



Surfaces. Surfaces. 



Interval between the surfaces of last molar 9.9 5.5 



Do. do. do. third molar, 9 8 5.5 



Do. do. do. second do 8.4 4.5 



Do. do. do. first do 6.4 3.2 



Space occupied by the line of molars 9.8 inches. 



Bones of the Head and Face. — From the age of the animal to which the 

 head had belonged, the bones had become anchylosed at their commis- 

 sures, so that every trace of suture has disappeared, and their limits and 

 connections are not distinguishable. 



The frontal is broad and flat, and slightly concave at its upper half. 

 It expands laterally into two considex-able swellings at the vertex, and 

 sweeps down to join the temporals in an ample curve ; and with no angu- 

 larity. It becomes narrower forwards, to behind the orbits ; and then 

 expands again in sending off an apophysis to join with the malar bone, 

 and complete the posterior circuit of the orbit. The width of the bone 

 where narrowest, behind the orbit, is very great, being 16.2 inches. Partly 

 between and partly to the rear of the orbits, there arise by a broad base, 

 passing insensibly into the frontal, two short thick conical processes. They 

 taper rapidly to a point, a little way below which they are mutilated in 

 the fossil. They start so erect from the brow, that their axis is perpen- 

 dicular to their basement : and they diverge at a considerable angle. From 

 their base upwards they are free from any rugosities, their surface being 

 smooth and even. They are evidently the osseous cores of two intra- 

 orbital horns. From their position and size they form one of the most 

 remai-kable features in the head. The connections of the frontal are no- 

 where distinguishable, no mark of a suture remaining. At the upper end 

 of the bone the skull is fractured, and the structure of the bone is exposed. 

 The internal and outer plates are seen to be widely separated, and the 

 interval to be occupied by large shells, formed by an expansion of the diploe 

 into plates, as in the elephant. The interval exceeds 2| inches in the 

 occipital. On the left side of the frontal, the swelling at the vertex, has its 

 upper lamina of bone removed, and the cast of the cells exhibits a surface 

 of almond-shaped or oblong eminences, with smooth hollows between. 



The temporal is greatly concealed by a quantity of the stony matrix, 

 which has not been removed from the temporal fossa. No trace of the 

 squamous suture remains to mark its limits and connection with the fron- 

 tal. The inferior processes of the bone about the auditory foramen have 

 been destroyed, or are concealed by stone. The zygomatic process is long, 

 and runs forward to join the corresponding apophysis of the jugalbone, 

 with little prominence or convexity. A line produced along it would pass 

 in front, through the tuberosities of the maxillaries_, and to the rear along 

 the upper margin of the occipital condyles. The process is stout and 

 thick. The temporal fossa is very long, and rather shallow. It does not 

 rise up high on the side of the cranium : it is overarched by the cylinder- 

 like sides of the frontal bone. The position and form of the articulating 

 surface with the lower jaw are concealed by stone which has not been 

 removed. 



-There is nothing in the fossil to enable us to determine the form and 

 limits of the parietal bones ; the cranium being chiefly mutilated in 

 the region which they occupy. But they appear to have had the same 

 form and character as in the ox : to have been intimately united with 

 the occipitals, and to have joined with the frontal at the upper angle 

 of the skull. 



The form and characters of the occipital are very marked. It occu- 

 pies a large space, having width proportioned to that of the frontal, and 

 considerable height. It is expanded laterally into two alae, which cona- 



G 



