136 MAEINE EEPTILES OF THE OXTOED CLAY. 



vertebrae from those of the other species is the great height and width of the neural 

 spines on the hinder part of the neck. The shoulder-girdle (PL VI. fig. 3 ; text-fig. 68) 

 is ossified completely on the Elasmosaurian plan. The scapulae are notable for the great 

 antero-posterior extent of the ventral rami ; these unite in a long symphysis posteriorly, 

 but are separated anteriorly by a deep notch, which was covered in front by the over- 

 lying interclavicle, while the posterior part of the notch forms the greater part of the 

 interscapular foramen [i.s.f), closed in front by the posterior border of the interclavicle. 

 The clavicles are represented by thin plates of bone adherent to the visceral face of the 

 interclavicle ; their free portions are not preserved in any specimen. The humerus and 

 femur seem to be proportionately rather shorter and stouter than in M. leedsi. 



The skeleton in this species may attain a great size and degree of massiveness, 

 equalling, or perhaps even surpassing, in this respect the largest specimens of 

 M. durobruensis (see measurements of R. 2425). 



R. 2678 (Leeds Coll. 12). Greater part o£ a skeleton o£ a large individual in which the ossification 

 of the shoulder-girdle and the fusion of the cervical ribs are complete. The parts 

 preserved are:— Skull (PI. VI. fig. 1), mandible (PL VI. fig. 2; text-fig. 48), thirty- 

 eight cervical vertebrse (PI. VI. figs. 4, 5), tvs'euty-one dorsals, fourteen caudals, 

 numerous dorsal and caudal ribs, (?) chevrons, shoulder-girdle (PL VI. fig. 3 ; text- 

 fig. 68), humeri (text-fig. 69 A), radius, ulna, and other bones of the paddle, pelvic 

 girdle, femoi-a (text-fig. 69 B). Type specimen described and figured by Seeley iu 

 Proc. Roy. Soc. vol. li. (1892) pp. 139-141, figs. 6, 7. 

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



SkuU (PL VI. fig. 1) : 



Approximate length on mid-dorsal line 27'0 



Length from pineal foramen to tip of snout 19-3 



Width of froutals between the orbits .... (approi.) 4-6 



Vertical diameter of the occipital cond3'le 2-8 



Length of basioccipital 4-4 



„ basispbenoid 3'8 



Mandible (PI. YI. i:g. 2 ; test-fig. 48) : 



Extreme length (approx.) 41-0 



Length of symphysis (crushed) 6'0 



Depth at coronoid process 7'4 



Width of articular surface for quadrate 3-0 



Cervical vertebrsE "I Anterior. Middle. Posterior. 



(PI. VI. figs. 4, 5, 5 a, 5 6) J — (Fig. 5.) (Fig. i.) 



Length of centrum iu mid- 

 ventral line 4-4 4-S 5-0 5-8 6-2 6-3 



Width of posterior end of 



centrum 4-9 5-3 5-5 6-4 ? ? 



Height of ditto 3-9 4-2 4-4 5-3 ? ? 



Height to top of neural spine 9-3 9-6 10-2 (app.) . . 18-8 21-0 



The dorsal vertebras are too much crushed for useful measurements to be made. 



