williston: new cretaceous turtle. 13 



apposition with the end of the transverse process of the sacrum. On 

 the left side, the ischium and a part of the ilium, also in position are 

 alone represented. Unfortunately of those of the right side the 

 outer end of the ilium and a part of the anterior border of the pubis 

 have been lost. The ilium is an irregular rod of bone, stout and not 

 very broad with a pointed sacral extremity. Its anterior border is 

 deeply concave, smooth and rounded, and not very thick. Its poste- 

 rior border is dilated into a thinner expansion below, which is turned 

 outward. Near the extremity, however, the bone again forms one 

 plane and is moderately thick. 



Greatest width of ilium 35 mm. 



Width before the acetabular articulation 26 " 



On the inner margin near the tip, there is a slight roughening, 

 lying in apposition to the tip of the transverse process of a sacral 

 vertebra. 



Ischium (fig. la). 



The ischia have a smooth paddle-shaped extremity, a long tooth- 

 like tuberosity, and a dilated articular extremity which shows facets 

 for the ilium and pubis. The symphysial end is broad, nearly 

 straight on its margin, with rounded angles, and moderately thick. 

 The tuberosity, which is situated about the middle of the bone, is 

 conical, pointed and curved toward the acetabulum. 



Length 84 mm. 



Width of symphysial end 43 



Width of acetabular end 35 



Width of shaft on the proximal side of the tuberosity 21 

 Length of tuberosity 25 



Pubis (fig. lb). 



The pubis is much thickened at the acetabular end, expanded and 

 thin at the symphysial end. The side exposed, the inner, shows two 

 facets, separated by a distinct angle. The ischial border is deeply 

 concave, and for the most part thin. The bone is narrowest midway, 

 and the whole lower part is evidently thin. Unfortunately the ante- 

 rior inferior portion has been lost. The surface exposed is nearly 

 plane throughout, though it probably had some curvature. There 

 are no indications on either pubis or ischium of union with the plastron. 



Width of acetabular extremity 37 mm. 



Length of ischial facet 25 



Length of bone as preserved 108 



Femur. 



The only bone of the hind extremity preserved is an incomplete 

 femur which lies directed backwards, with the great trochanter imme- 

 diately below the sacral end of the ilium. Its great trochanter is 



