4 FOSSIL REPTILIA OF THE 



family. The ramus has a less relative depth than in Brachydectes minor, fig. 3 ; it 

 measures in extreme vertical extent, taken at about one fourth of the length from the 

 angle, 1 inch 9 lines, or little more than one sixth the entire length of the ramus, 

 whilst in Br. minor the extreme depth of the mandible, which is about midway between 

 the two ends, is nearly one fifth of the entire length of the ramus. This proportion 

 might, however, be deemed an immature character of the smaller specimen, but there are 

 other differences in the jaw of Brachydedes m.ajor not attributable to age and conse- 

 quent growth. There is no longitudinal ridge on the angular element. The angle 

 itself is more produced. This process repeats, indeed, the low position characteristic of 

 the genus Brachydedes, but the line descending thereto from the articular element is 

 straight, not concave, as in Br. minor, and the curve from the angle to the convex border 

 of the angular element (fig. 1, so) is deeply concave. Moreover, the outer surface of the 

 deep hinder part of the ramus is sculptured with close-set deep pits, giving a strongly 

 reticular character to that part of the bone. 



The alveolar tract shows, as in Brachydedes minor, a laniary convexity {I) as well as 

 an incisive one (i) ; both, however, are slight. In the latter the crown of the third or 

 fourth incisor is preserved ; it is 20 mm. in length, 6 mm. in basal breadth. The 

 enamel of the exposed outer side is smooth ; the fore part of the crown is obtuse, the 

 hind part trenchant, with a faint appearance of minute denticulation. This is the only 

 tooth preserved in the present jaw. There are faint indications of ten or twelve alveoli 

 behind the tooth ; two of these in the laniary curve (l) indicate teeth proportionally as 

 large as the canine in Brachydedes minor. The outer surface of the laniary convexity is 

 smooth. The rugged irregularly and minutely pitted character is continued to the 

 alveolar border of the incisive convexity. The sutures between the dentary and hinder 

 elements of the mandible are not clearly definable. Certain parts of the outer surface 

 which were wanting made it doubtful wdiether any vacuity between the surangular, 

 angular, and dentary elements existed ; and the condition of the jaw of the smaller 

 species weighs in favour of assigning an uninterrupted outer wall of the mandible as an 

 additional diff"erential character of the genus. 



The proportion of the incisor tooth approaches that of the third in Petrosuchus} but 

 the latter is longer in proportion to the basal breadth. The dental series, and conse- 

 quently the dentary element, are relatively longer in Petrosuchus than in Brachydedes. 



A second specimen of the left dentary bone repeats closely the same size and 

 characters of the corresponding part of the mandibular ramus above described. The 

 teeth are wanting. Behind the alveolus of the ' anterior canine ' are indications of 

 seven or eight following alveoli, not more. The better preserved outer plate of the bone 

 demonstrates the absence of the vacuity which is present in Petrosuchus, Goniopholis, 

 and Crocodilia generally. 



1 ' Supplement ' (No. viii), pi. vi, fig. 3. 



