from the Oxford Clay of Peterborough. 305 



The upper teeth are about tliirty-four in number. The 

 premaxillae bear four each, of which the first two are small, 

 crowded together, and directed forward ; the third and fourth 

 are large and their alveoli separated by four or five millimetres 

 only. Behind these there is a short, concave, edentulous 

 space ; then follows the series of 29-30 maxillary teeth, which 

 are relatively large, and are separated by intervals less than 

 the diameter of their alveoli. The teeth are directed down- 

 ward and a little forward. 



The rami of the mandible are stout ; they pass into the 

 symphysial region by a gentle curve. The symphysis reaches 

 back to the 25th tooth and the splenials extend forward in it 

 to the level of the 17th tooth. Both the upper and ventral 

 surfaces of the symphysis are nearly flat; there is a slight 

 expansion between the enlarged third and fourth teeth ; at 

 the anterior end the line of junction of the two rami is marked 

 by a deep median notch. 



The first two lower teeth were small and directed nearly 

 straight forward ; the third and fourth are the largest in the 

 jaw and are closely crowded together. Behind these there is 

 a short diastema ; then comes a series of about 27 teeth, a few 

 of those in the front and close to the back being somewhat 

 smaller than the others. They appear to have been directed 

 upward and a little forward. 



No good specimen of the teeth, either upper or lower,, has 

 been seen, all having either fallen from their sockets or been 

 broken off short. Judging from some of the replacing germs, 

 the crown would appear to have been blunter than those of 

 the species described above, but much less so than is the case 

 in the next species. 



The dimensions of the skull and mandible in the type 

 specimen of Steneosaurus durohrivensis are : — 



Skull. cm. 



Total length 74 



Length in front of orbit 45 



Width between outer angles of quadrate 24* 



Length of temporal fossae (inner side) 18 



Width „ „ „ 8-8 



,, of frontals between orbits 5'4 



„ of middle of snout 6*4 



,, behind premaxillary expansion 4'8 



„ of premaxillary expansion 5'7 



* Wider than in life, owing to the crushing outwards of the quadrate. 



