MUE.ENOSAUEIJS DUROBEIVENSIS. 129 



and tlie condition of the proximal ends of the humerus and femur) until a much greater 

 size has been attained than in M. leedsi, and all parts of the skeleton are more massive 

 than in that form, xinother point is, that the expansion of the distal end of the 

 humerus is greater than in M. leedsi. 



As already noticed, the cervical vertebrae are shorter than in M. leedsi; and this 

 difference is most marked in the posterior part of the neck, where the centra in the 

 present species are shorter in comparison with those of the anterior region. The 

 plications on the edges of the centra, just outside the articular faces, are particularly 

 well marked in this species, certainly much more so than in M. platyclis, where they 

 seem to be replaced by irregular rugosities. It was the existence of these plications on 

 a cervical vertebra that caused Phillips to name one of the Oxford Clay Plesiosaiirs 

 Plesiosauriis plicatus : this no doubt is a Muroenosaurus, but it is not possible on the 

 available evidence to be sure whether it is identical with the present species or with 

 M. leedsi or is a distinct form. In the pectoral girdle in this species the median union 

 of the scapulae with one another does not take place till a very large size has been 

 attained, and the median junction of the coracoids and scapulae was still later. The 

 interclavicle is a small oval bone, with anterior and posterior rounded notches in the 

 middle line ; it is thickened in the middle, especially towards the anterior border, but 

 laterally it thins out to a sharp edge ; no trace of clavicles has been observed. 



E. 2428 (Leeds Coll. 28). Portion of a skeleton, including twenty-nine cervicals (PL V. figs. 1-3), 

 two pectorals, fourteen dorsals (PI. V. figs. 4, 5), and some caudals (PI. V. figs. 6, 7); 

 coracoids and scapulae (text-fig. 67) ; imperfect fore paddles ; ilia, ischia, and one pubis 

 (text-fig. 65) ; incomplete hind paddles. Type specimen referred to by Lydekker in 

 Catal. Foss. Rept. Brit. Mns. pt. ii. (1889) p. viii. The pectoral and pelvic girdles have 

 been described and figured in Ann. Mag. Nat. Hist. [6] vol. xvi. (1895) as those of 

 of M. plicatus, Phillips, sp. 



In this specimen the neural arches are wanting in all but two or three of the 

 vertebrse, and in the cervical region the ribs are also missing, fusion with the centrum 

 not having taken place in either case. The ventral rami of the scapulse have not vet 

 reached the middle line and are widely separated from the coracoids, so that there is no 

 doubt that although this was a large individual it had not nearly attained its full size. 



The dimensions (in centimetres) of some of the bones of this skeleton are as follow : — 



Vertebral contra. 1 Anterior Middle Posterior First dorsal -j, ^ , Caudals Caudals 



(PI. V. figs. 1-7.) J cervicals. cervicals. cervicals. crushed. ' ' anterior. posterior. 



Length in mid-ventral line . 2-7 4-0 4-9 5-0 5-3 5-2 5-5 5-.5 o~ 4-2 2-S 2-5 

 Width of posterior articular 



surface SI 4-2 5-7 6-0 7-1 7-2 7-4 7-2 7-2 6-5 4-3 37 



Height of posterior articular 



surface 2-5 3-4 4-6 5-2 57 57 6-2 6-0 6-4 4-9 3-5 3-1 



iScapula (test-fig. 67) : greatest length ........ 27-4 



length from anterior angle to posterior 



end of ventral ramus 16-8 



