AND AVES OF NORTH AMERICA. 



93 



Depth of glenoid cavity, 



Width " 



" " anterior expansion, 

 " " fractured end, 



In. 



3.4 



3.16 



4.22 



1.8 



Another fragment of an animal of dimensions similar to the last was found at the same 

 time and at or near the same place, (Freehold,) in Monmouth county, New Jersey, but 

 cannot be associated with the above described scapula, as neither the place nor time of dis- 

 covery can be ascertained with sufficient accuracy. It appears to be the glenoid cavity of 

 a scapida from which the blade has been broken off, and from which a short subconic 

 procoracoid projects. The accompanying cut and measurements will furnish the requisite 

 information respecting it. 



Fig. 28. 



Length from a to b, 



" " b to c, 



" d to e, 



" e to f, 



Inches. 

 5.54 

 7.22 

 4.71 

 3.53 



The fragment may belong to Mosasaurus. 



Pelvis. — There is much difficulty in determining the true relations of the pelvic ele- 

 ments of these and other Dinosauria, owing to their unusual forms, our imperfect materials, 

 and the discrepancies between authors. 



Ilium. — One of our best clues is the skeleton of the Iguanodon discovered at Maid- 

 stone, and preserved on a block of rag, which has been described and figured by Professor 

 Owen. The bones mostly preserve a normal though much disturbed relation to each 

 other. An examination of the figure and description strongly suggests — 



First, that the hooked superior prolongation of the ilium is the posterior, not the an- 

 terior, as described by Owen. This is confirmed by Owen's figure and description of the 

 ilium and sacrum of the same species in Wealden Reptiles, PI. III. (Iguanodon), where 

 the thick hook-like process with its abrupt descent to the acetabulum, is also posterior. 



• The structure of Hadrosaurus, in which both caudal and lumbar vertebra? have been 

 discovered, proves that this relation is the true one. The caudals have a greater trans- 

 verse diameter than the lumbars, which are comparatively quite contracted from side to 

 side. This is the reverse of what is usual among reptilia, where the caudals are usually 



AMERI. PHILOSO. SOC VOL. XIV. 24 



