ON BRITISH FOSSIL REPTILES. 151 



lines. Near this chain of four and a smaller part of a fifth vertebra, there 

 are portions of four ribs. These have a single, not a bifurcated head ; they 

 are subcompressed, slightly and pretty uniformly curved, and grooved longi- 

 tudinally on both sides ; the longest portion of rib measures 2 inches, follow- 

 ing the curvature. The same fragment of sandstone contains three flat bones, 

 which offer several striking modifications, whether they be compared with the 

 constituents of an os innoniinatum or of the scapular arch. 



The most entire of the three bones consists of a thicker articular end ; 

 a long, broad and thin plate, forming the body of the bone ; and a mode- 

 rately long trihedral process, given off from the convex margin near the 

 articular end. In these characters the comparative anatomist conversant 

 with the modifications of the skeleton in recent and extinct Saurians will re- 

 cognize a resemblance to the scapula of the Iguanodou and Hylaeosaur, in 

 a minor degree to the ischium of the Crocodile, and somewhat more remote- 

 ly, to the pubis of the Tortoise. The trihedral process, in the second compa- 

 rison, would match the anterior pubic process of the Crocodile's ischium, 

 but the entire bone would differ from that of the Crocodile in the slender- 

 ness of the pubic process, in the greater breadth and less length of the body 

 of the bone, and in its extreme thinness ; it increases in thickness, however, 

 as in the Crocodile's ischium, towards the articular end. The correspond- 

 ence of the trihedral process of the bone in question with the long spinous 

 process of the Chelonian pubis, is less close than the one just discussed. If 

 the present well-marked bone of the Rhynchosaur be regarded as a scapula, 

 it is to that bone in the Dinosauria that it offers most resemblance ; and the 

 prismatic process would then correspond with the one sent off from the an- 

 terior part of the coracoid articular surface in the scapula of the Hylaeosaur 

 and Iguanodon. It is the concavity at the neck of the bone, at the side oppo- 

 site that from which the process is sent, which gives it a nearer resemblance 

 to the Dinosaurian scapula than to the Crocodilian ischium ; it differs from 

 the scapula of tlie Crocodile in having the posterior margin, beyond the neck, 

 straight instead of convex ; the corresponding margin in the ischium being 

 concave. The blade of the bone, considered as scapula, is broader and shorter 

 than in either the Dinosaurs or Crocodiles. Its outer surface is slightly con- 

 vex : supposing it to be placed vertically upon the thicker articular end, the 

 prismatic process is directed forwards and downwards. There are a few small 

 pits or inequalities near the neck or thick articular margin in the present fossil. 

 The outer surface of the plate is marked with extremely fine striae, radiating 



from the neck. , , • 



In. Lm. 



Length of the bone 18 



Breadth of neck 5^ 



Breadth of base 10 



Length of trihedral process 8 



Coracoid. — The remains of a thin and broad plate of bone, attached by a 

 short neck to an apparently articular thickened head or process, might be 

 compared with a coracoid, as it resembles, so far as it is preserved, the cora- 

 coid of lizards, more than it does any other known bone; there is not, how- 

 ever, the perforation near the articular surface. The breadth of the neck is 

 6 lines, that of tiie body of the bone which remains 13 lines ; the length, or 

 diameter at right angles to the above, is 10 lines ; the bone is tliinned off to 

 an edge, which is gently convex. 



Humerus. — A tiiird bone, imbedded in the same piece of sandstone at a 

 little distance from the preceding, is expanded at both extremities, contracted 

 and twisted in the middle ; one of the expanded extremities, apparently the 



