MYOMORPHA. 859 



temporal ridges, and a delicate raised line represents the sagittal crest. The 

 muzzle is wider above than below, and the superior and lateral faces are 

 separated by a distinct angle, which is acute on the posterior half. In front 

 of the superior part of the orbit is a fossa, which is directed obliquely up- 

 wards and forwards. The fundus of the orbit is not as large as in some 

 species, giving a greater depth to the maxillary bone, which is ah indication of 

 length of the prisms of the superior molars. The palatal surface has two 

 gi'ooves, each of which is continued into a pterygoid fossa. The otic bullae 

 are rather small for the genus, and are flattened behind. Anteriorly they 

 are continued into a neck on each side, which meets its mate of the opposite 

 side on the middle line, resting on the basisphenoid bone. Each neck is 

 pinched off backwards, so that the two inclose an angle between them. 

 The tympanic or meatal tube in this species is very long, exceeding that of 

 any other species, and equaling the long diameter of the bulla witliout the 

 anterior neck. The mastoid adheres closely to the posterior side of the 

 tube, extending to its extremity, and separated from it on the inferior side 

 by a groove. The posterior side of the mastoid is triangular in form, and 

 is nearly flat. Inferiorly there is no groove marking its point of separation 

 from the bulla ; superiorly it carries a strong angle from the inion to its 

 external extremity. The superior face of the brain-case is nearly flat. The 

 occiput is vertical, slightly concave between the points of junction with the 

 mastoid, and with a slight median keel above. The foramen magnum is 

 large, subquadrate, and a little wider than liigh. The basioccipital supports 

 a median keel, and is concave on each side in front of the condyles. 



The supraoccipital bone has a rather wide triangular exposure. The 

 parietals diverge from the middle line anteriorly, and the suture reaches the 

 squamosal near the posterior border of the orbit. The posterior extremity 

 of the nasal bones reaches that of the premaxillai-ies, and both terminate in 

 line with the deepest part of the preorbital fossa. 



The superior molar teeth display the typical characters of the genus. 

 Each has an external groove for part of its length, and the anterior column 

 of the last premolar has no anterior production, but has the form of the 

 other teeth. The sizes are, commencing witli the largest, 2-1-3-4. 



The inferior edge of the angular portion of the mandible is strongly 

 inflected, and the interior face below the molars is concave. The inferior 



