CONDYLARTHRA. 429 



and squamosal. Alisphenoid joining the parietal. Lachrymal bone larger, 

 extending anteriorly and posteriorly to the anterior border of the orbit. 



Incisive and infraorbital foramina present. Lachrymal foramen not 

 exterior to the orbit. An alisphenoid canal, into which the foramen rotundum 

 opens. Foramen ovale separated from the foramen laceriim anterius. A' 

 postglenoid foramen. Carotid foramen grooving the side of the basioccip- 

 ital bone forwards and upwards. The condition of the foramina lacera 

 uncertain, owing to the loss of the petrous bones Foramen condyloideum 

 distinct. Postparietal and supraglenoid foramina present. 



The mandibular rami are not coossified at the symphysis. The con- 

 dyle is elevated, standing a considerable distance above the line of the 

 molar teeth, and its articular surface looks mostly upwards. On the inner 

 half it is decurved so that the posterior half looks posteriorly. The coro- 

 noid process is elevated, and the angular region is in the same vertical plane. 



The dental formula is: I. -; C. -; P-m. -: M. . The incisors have 



3 1 4 3 



transversely expanded sharp-edged ci"Owns. The canines are not very large. 

 The anterior pi-emolars are a little spaced, but there are no distinct diaste- 

 mata, except in P. primcevus, a short one behind the first inferior premolar. 

 The first premolar in botli jaws is one-rooted and has a simple crown. The 

 third and fourth superior premolars have internal lobes and two external 

 • cusps. The true molars have two internal, two intermediate, and two ex- 

 ternal tubercles. The external faces of the latter are convex. Anterior 

 cingular cusp rudimental. The third and fourth inferior premolars have 

 an internal median cusp, and the fourth is not like the first true molar. The 

 true molars support four cusps opposite in pairs, and an odd one between 

 and behind the posterior two. This tubercle is developed into a heel on the 

 last molar. 



The numbers of the vertebrae are C, 7 ; D, 14-15; L, H or 7 ; S, 3 

 or 5. The numbers are certainly known in P. vortmani, and also in P. 

 primcevus, excepting in the case of the dorsals. Of tliese there- are thirteen 

 preserved in the specimen of P. primcevus; one is probably lost from the 

 front of the series, and one, probably the thirteenth, from the posterior part 



