608 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 49. 



The acetabular arc ends anteriorly in a broad, but relatively light 

 pubic peduncle, being terminated posteriorly by a heavy swelling 

 which forms the articulation for the ischium. 



The external side of the ihum is shghtly concave from end to end. 



Measurements of ilium, No. 7757. 



Tmn. 



Greatest length of ilium 336 



Greatest length from posterior end to the center of preacetabular notch 193 



Greatest width over ischiac articulation 91 



Greatest width at middle of acetabulum 48 



Greatest expanse of acetabulum 78 



Pubis. — The prepubic portion of the pubis is an angularly rounded 

 rodhke bone that extends forward nearly parallel with the preace- 

 tabular process of the ilium, exceeding the latter in length. The 

 acetabular end is thick and heavy and above is closely united with 

 the peduncle of the ilium. Below this acetabular portion is an oval 

 foramenal notch, that in an aged individual would doubtless become 

 closed as it has in the pubis of Hypsilophodon. The postpubis is a 

 long, slender, rodlike bone that reaches the end of the ischium. 

 It is rounded as in Camptosaurus, and contrasted with the postpubis 

 of Hypsilophodon, it is more flattened with a somewhat heavier shaft. 

 In the type-specimen the distal extremities of the postpubis are 

 missing but the impression of these bones in the matrix shows their 

 exact length and also gives a good idea of their size and rounded 

 shape, as indicated in figure 17. 



Measurements of pubis, No. 7757. 



mm. 



Greatest length of prepubis 192 



Greatest length of postpubis ' 516 



Greatest width of pr-^pubis 11 



Greatest depth of prepubis 19 



Ischium. — The ischium is a long, slender, somewhat flattened bone, 

 that when articulated is directed backward and downward from 

 the ihum. The proximal end is moderately expanded with two 

 distinct articular ends. The anterior one which articulates with the 

 pubis and the heavier one that meets the ischiac peduncle of the 

 ihum is shown in figure 17. The upper concave border between 

 these two processes forms the greater portion of the lower boundary 

 of the acetabulum. Below the head, the shaft contracts rapidly 

 but again widens on the infero-internal border into a thin, narrow, 

 upturned obturator process which curves up under the slender 

 postpubis. This process is much more elongate and placed more 

 distally than in Camptosaurus, but resembles Hypsilophodon in both^ 

 these respects. 



1 E^stimated, 



