366 PROFESSOR OWEN, ON THE RHYNCHOSAURUS. 



contracted and twisted in the middle. One of the expanded extremities, 

 apparently the proximal end, is nearly entire: it terminates by an irre- 

 gular convex border not thinned off to an edge, but adapted to the 

 formation of a joint, and to the attachment of cartilage. The exposed 

 surface of the expanded head is concave from side to side, somewhat 

 resembling the expanded and bent pubic plate in Lizards. The opposite 

 extremity is broken across : it shows the commencement of a slight longi- 

 tudinal ridge near its middle part. This bone bears most resemblance 

 to a humerus ; but I am at present unable to determine it unequivocally. 

 If compared with the left pubis of Lacertians, the entire and bent 

 extremity corresponds with the median portion of that bone; but the 

 middle part or stem is much longer in the fossil; and the broken end 

 which would agree with the acetabular end of the pubis, is too thin to 

 have entered into the formation of such a cavity in the fossil : it likewise 

 wants the perforation which characterizes the pubis in Lizards. The same 

 thinness and imperforate condition of the fractured end oppose the com- 

 parison of the present bone with the coracoid of the Crocodile: 



In. Lines. 



Length of this bone as far as complete 1 . 9 



Breadth in the middle . 3 



Breadth of entire expanded extremity . 10 



In the slab containing the above -described bones there are other 

 fragments of bone; but too small and imperfect for profitable description. 

 Those of which I have endeavoured to make the form and analogies in- 

 telligible, though evidently peculiar, as might be expected in a Saurian 

 with so strange a head, and perhaps with a hind toe directed backwards 

 as in Birds, may be regarded as most probably constituents of a strong 

 and well-developed pectoral arch, and a humerus : and they indubitably 

 indicate a mechanism for locomotion on land, which would agree with 

 that of the animal that has left the impressions of its footsteps upon the 

 same sandstone. 



Radius and Ulna. — Another piece of coarse-grained sandstone from 

 the same quarry contains a series of seven or eight vertebrae, in a very 

 fragmentary state ; also two or three ribs, rather more slender and not 



