MYCTEROSUCHUS NASUTUS. 141 



length of the femur and tibia be taken as 100, then the combined length of the humerus 

 and radius will be represented in Mycterosuchus nasntus by about 54, but in Steneo- 

 saurus leedsi and Steneosaurus durobrivensis by about 43. 



The pelvis is not known, and the bones of the hind limb, so far as preserved, do not 

 appear to differ much in structure from those of Steneosaurus. The tibia is just half 

 the length of the femur, while in Steneosaurus it is rather less. 



The dermal scutes (PL VIII. figs. 4, 10) are proportionately thicker and heavier 

 than in Steneosaurus. In the dorsal region the keel does not appear to have been 

 well developed ; the sculpture consists of a number of large, deep, and closely- 

 set pits. 



R. 2617 (Leeds Coll. 1). The greater part of the skeleton of a large individual, including nearly 

 complete but crushed skull and mandible (PI. VIII. figs. 1, 2), atlas, axis, and nine 

 other cervical vertebrae, two or three crushed dorsals, forty-two caudals (PL VIII. 

 figs. 4-9), left coracoid and scapula (text-fig. 54, C), left humerus (text-fig. 54, A, B) and 

 ulna, left and part of right femur, right tibia and fibula, astragalus, calcaneum, meta- 

 tarsals and other foot-bones. Numerous scutes are preserved, in many cases adherent 

 to the sides of the neural spines. Type specimen, the skull and mandible being 

 described and the skull figured in Ann. Mag. Nat, Hist. [8] vol. iii. (1909) p. ;!Ui. 

 pi. ix. fig. 1 (the registered no. is there wrongly given as R. 3577). 



The dimensions (in centimetres) of this specimen are : — 



Skull (PI. VIII. fig. 1): 



Total length 100-0 



Length in front of orbits 73-0 



Width between the outer angles of the quadrates .... 25-0 



Length of temporal fosss (inner side) 14-0 



Width of temporal fossa? 10-5 



„ of frontals between orbits 6-0 



„ of skull at anterior border of orbits 16-5 



„ at anterior angle of nasals 6 - o 



„ behind premaxillary expansion 4-2 



„ of premaxillary expansion 7'3 



Mandible (PI. VIII. fig. 2): 



Total length 110-0 



Length of symphysial portion 62-0 



Width at hinder end of symphysis 11-0 



,, behind anterior expansion 4-2 



Owing to the crushing undergone by the skull and mandible, many of the above 

 dimensions are only to be taken as approximate. 



