124 MARINE EEPTILES OP THE OXFOED CLAY. 



E. 2424 (Leeds Coll. 23). Imperfect skeleton, the skull and mandible being entirely absent. The 

 vertebral column is represented by thirtj'-four eervicals, two pectorals, twenty-three 

 dorsals (includino- two sacrals), and eighteen caudals. In some cases tl;e centra are 

 much crushed and in all are separated from the neural arches, cervical and caudal ribs, 

 etc. Five complete neural arches (four dorsal and one caudal), with portions of several 

 others, are preserved. Several cervical ribs and several more or less nearly complete 

 dorsal ribs are present. The right humerus with the radius and ulna, two ischia, part 

 of a pubis, both femora, with some other bones of the hind paddle are preserved. 



In this specimen ossification is not so far advanced as in the type, although it is 

 already larger, so that probably this individual might have attained a considerably 

 greater size than the type. In the form of the limb-bones, so far as known, the two 

 are closely similar, but in the cervical vertebrae, especially in the posterior members of 

 the series, there are some differences, the most striking being that the width of the 

 centrum is somewhat greater in proportion to the height. It must be noted, however, 

 that in the type specimen many of the vertebree have been distorted by pressure, and 

 this may account for the dissimilarity. 



Associated with this skeleton and in exactly similar condition of preservation is a 

 clavicle (figured by Seeley in Proc. Roy. Soc. vol. li. (1<:!92) p. 141, fig. 8) of an 

 irregular triradiate form, its irregularity of outline probably indicating that the 

 clavicles were undergoing reduction. "With the exception of a portion of the opposite 

 clavicle, this bone is the only element of the shoulder-girdle preserved in this specimen, 

 and no such bone has been found with any other Jllurcenosaurus-skeleiou, so far as I am 

 aware, so it is just possible that it may actually belong to a species of Cryptoc.leidus. If, on 

 the other hand, this is not so, and the bone is actually that of M. leedsi, it indicates 

 that in some cases the clavicles undergo much less reduction than usual, and that this 

 species must, in the structure of its clavicular arch, have been much like M. platyclis. 



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



,- , , P ■ , , Fift!-. Tenth Sixteenth ^'":<^"f-^- ^if'^^- ^"'''5,- 



\ertebr,T: UerTieals* . , . , . . sixth nllh second 



eerMcal. cerviual. cei-vical. , ■ , ■ , 



Cervical. cer\ical. cervical. 



Length of centrum in mid- 



ventralline 3-4 4-2 5-1 5-2 5-3 5-2 



Width at posterior end . . 34 4-3 4-7 56 63 67 



Height at posterior end . . 2-6 3-4 4-1 4-8 4-8 4-8 



Caiicluls Anterior. Posterior. 



Length of centrum on mij-veutral line .... 3-6 3-4 



Width at posterior end 5-4 o-l 



Height at posterior end 4-0 4-0 



llumertis : length 27'5 



width of head 6-8 



greatest width of proximal end 9-0 



least antero-posterior diameter of shaft .... 7'3 



width of distal end 16-2 



* The numbers of the eervicals in the series are only approximate. The dorsals are all too much 

 crushed for measurement. 



