f)'om tlie Oxford Clay of PeterhorougJi. 303 



slender, sharp-pointed, and the enamel is markel by a series 

 of very fine longitudinal ridges with a ratiier stronger and 

 more continuous ridge on the outer side. 



The mandible is slender and compressed vertically. The 

 palatal surface appears to have been somewhat convex. The 

 ventral surface is marked by an ornamentation of irregular 

 longitudinal ridges. There is a slight anterior expansion and 

 the third and fourth teeth are enlarged ; there are 42 teeth 

 on either side and their structure is similar to that of the 

 upper teeth. The splenial extends into the symphysis as far 

 as the twenty-second tooth. The posterior (ventral) limit of 

 the symphysis is opposite the tliirty-seventh tooth. 



This species approaches S. leedsi m the length of its snout, 

 the preorbital portion of which is about 73 per cent, of the 

 whole length of the skull in both species ; in the next species, 

 S. durobri'vensis, it is only about 61 per cent. In the number 

 of teeth it also resembles S. leedsi and ditFersfrom S. durohri- 

 vensis, in which the number is smaller. On the other hand, it 

 is sharply distinguished from S. leedsi by the shorter temporal 

 fossa?, the position of the orbits and the strong sculpturing of 

 the frontal bones; and the first two of these characters at least 

 separate it from S, intermedins, S. edwardsi, and S. heherti, 

 from all of which it differs further in the possession of a 

 greater number of teeth. 



The dimensions of the type skull and mandible of Steneo- 

 saurus nasutus are : — 



Skull. cm. 



Total length 100 



liength in front of orbits 73 



Width between outer angles of the quadrates .... 26 



Length of temporal fossae (inner side) 14 



Width „ „ „ 10-5 



„ of frontals between the orbits 6 



,, at anterior border of orbit 16-5 



„ of middle of snout 63 



„ behind premaxillary expansion 4*2 



„ of premaxillary expansion 7 '3 



Ma7idible. 



Total length 110 



Length of symphysial portion 62 



Width at hinder end of symphysis 11"6 



,, immediately behind anterior expansion . . 42 



Owing to the crushing that the specimens have undergone, 

 many of the above measurements can be regarded as approxi- 

 mate only. 



21* 



