14 Mr. A. S. Woodward on some 



width of the mandibular symphysis, the remarkable reduction 

 of the tritoral areas, and the prominence of the median tritor 

 that remains. 



Pachymylus Leedsi, sp. n. (PI. III. figs. 1, 2.) 



Diagnosis. — A species attaining to a large size, the 

 measurement from the middle of the symphysial border to 

 the extremity of the post-oral margin of the type mandibular 

 tooth being 0*14 m. Mandibular tooth with a proaiinent 

 beak, and the symphysial facette occupying about one third 

 of the inner aspect ; median tritor narrow, occupying only 

 one sixth of tlie length of the oral face ; posterior outer tritor 

 reduced to three small, round, punctated areas. Palatine 

 tooth diverging from its fellow of the o]iposite side in front, and 

 terminating anteriorly in a sharp, chisel-like edge ; median 

 tritor occupying much less than half the width of the tooth 

 and separated by a space equal to its own length from the 

 anterior border. [^Vomerine tooth unknown.] 



Eemarks. — This, the type species of the genus, is based 

 upon the mandibular tooth and the pair of palatine teeth 

 shown of two thirds the natural size in PI. III. figs. 1, 2. 

 The state of preservation of all the specimens is good, the 

 hinder border only of the palatine teeth being partly destroyed. 

 Viewed from the oral aspect (fig. 1) the palatine teeth exhibit 

 a slight want o£ symmetry ; and there is a marked line of 

 weakness round the elevation on which the tritor is placed, 

 this line being indicated by the fracture in the tooth of the 

 left side. The inner face of each palatine tooth (fig. 1 h) 

 exhibits the fibrous texture of the cement and exposes the 

 base of the tritor in irregular, narrow, oblique stripes ; the 

 outer face (fig. 1 a) shows the strengthened external border, 

 while the tritoral prominence is also conspicuous from this 

 aspect. Seen from the inner face (fig. 2) the mandibular 

 tooth exhibits its robust character ; and a direct view of the 

 symphysial facette (fig. 2 a) shows its very broad rhomboidal 

 form. The external oral border of the mandibular tooth is 

 strengthened, but not far beneath this border the outer face 

 in the fossil is crushed and destroyed. 



Formation and Locality. — Oxford Clay, Peterborough. 



Genus Beachymylus, nov. 



Diagnosis. — Mandibular tooth short and deep, much 

 laterally compressed, the symphysial facette narrow, and the 



