FROM THE OXFOED CLAY OF PETERBOROTJGH. 287 



length of the Kimeridgian mandible is 52 inches, the portion of the 

 symphysis in advance of the extremity of the splenials being one 

 fifth of the whole length. Calculating the dimensions of the present 

 mandible on these proportions we should have a total length of 

 about 25 inches. 



The resemblance to the above-mentioned jaw which I have refer- 

 red to Machimosaurus mosce is, indeed, so close, that were it not for 

 other evidence, I should have been inclined, in spite of its much 

 smaller dimensions, to regard the present specimen as indicating 

 another representative of the same genus. 



In his collection Mr. Leeds has, however, an imperfect crocodilian 

 skull from the Oxf ordian of Peterborough, which appears, both to him 

 and to myself, to belong to the same form as the present specimen, 

 and which certainly cannot be referred fco Machimosaurus. The 

 mandible of that specimen agrees precisely in size with the one 

 before us, and has a symphysis of just the same length : unfortu- 

 nately, however, it has been crushed in the opposite direction, that 

 is to say, the symphysial region has been compressed from side to 

 side, so as to render comparison of details almost impossible. Ten 

 alveoli can now be traced in the right ramus, some of which still 

 retain their teeth ; and it is quite probable that there may have 

 been two or three more. There is no trace of a long interval 

 between the 4th and 5th alveoli, and I have accordingly little 

 or no hesitation is regarding this skull as specifically identical with 

 the detached mandible. The cranium of the second specimen has 

 the laterally placed orbits characteristic of Metriorliynclius, and it 

 approximates in contour to the cranium from the Oxfordian of Nor- 

 mandy, figured by E. Deslongchamps in his ' Notes Paleontologiques,' 

 pi. xxiii. as MetriorliynGlius hrachyrliynclius. The English cranium 

 has, hovrever, a broader muzzle than in the latter, the nasals are 

 relatively shorter and wider, and do not reach the premaxillse, and the 

 number of teeth was evidently considerably less, although the exact 

 number cannot be determined. If Deslongchamps is correct in his 

 restoration of the missing muzzle of M. hracliyrhynclius^ there must 

 have been at least 20 upper teeth, while in the present form, cal- 

 culating from the lower jaw, there were probably only some 15 

 teeth in the upper jaw. The mandible and teeth of M. hrachy- 

 rhynchus are unknown, and since the restoration of the muzzle is 

 conjectural, it is quite possible that it may have differed considerably 

 in these points from the more typical representatives of the genus, as 

 it certainly does in the shortening of the rostrum. The teeth of the 

 skull in the Eyebury Collection (diagram, fig. 3) are distinguished 

 from those of MetriorhyncJms (ibid. fig. 4) by their more compressed 

 and expanded crowns, of which the enamel is nearly smooth, instead 

 of having the strongly marked vertical striae which are so character- 

 istic of those of the latter. The teeth of the present form are, indeed, 

 more like those of Geosuurus (Daeosaurus) , although readily distin- 

 guished by the absence of serrations on the fore-and-aft carinie. 

 These teeth, it may be observed, agree precisely in size with the 

 alveoli of the figured mandible. 



