86 



The anterior and lateral portions of the pubes are very thin, as are also 

 the median posterior portions of the ischiadic plates. The pubic bones are 

 thickest on the posterior margin ; they present a downward-projecting median 

 convexity near the anterior end. Depth of the articular face, 2 inches 8 

 lines. 



The superior surface of this arch was brought to light by the exertions 

 of my friends B. Waterhouse Hawkins and William M. Gabb, who removed a 

 large mass of matrix, which fortunately protected and accompanied it. This 

 presents a transverse thickening extending across it, and continuous with the 

 posterior margin of the clavicles. A median longitudinal thickening extends 

 from this to the anterior emarginalion, embracing in its angle with the trans- 

 verse a shallow concavity. The posterior projection, which is continuous 

 with the median part of the ischia, is strongly dellexed behind the transverse 

 rib, and is continuous with the basinlike concavity formed by the united 

 pubes. The glenoid surface of the pubes is a sigmoid, while that of the 

 ischia is regularly convex. The articulation of the ilium has been exclusively 

 with the former. 



Of the pleurapophysial portion of the two arches nothing appears to be 

 preserved except two lateral symmetrical long bones. One was found em- 

 bedded in the mass carrying the pelvic arch, and they articulate well with 

 the pubes ; but the articular extremity is too short to articulate with ischia at 

 the same time. Though they resemble the inferior view of the procoracoids, 

 they represent the ilia of Plesiosaurus. The head is subdiscoid, rather Hat, 

 slightly projecting eccentrically with a ligamentous pit. The articular surtace 

 is very oblique to the axis of the shaft, and is separated from the surtace by 

 a marked angle all round. Nothing like a trochanteric ridge is apparent in 



this bone. 



Measurements. 



Inches. Lines. 



Length iu the middle of the curve 9 y 



Diameter at tho bead : :5 :{ 



Diameter, distally, on the curve <i 



Diameter, distally, straight 1 



The shaft is Battened cylindric ; much tlattened nearest the proximal 

 extremity. The latter is very oblique to the shaft, and slightly convex near 

 the proximal margin. 



The end of the muzzle preserved includes also the symphysis and pails 

 of the rami of the mandible. The parts have been crushed together, and the 



