moodie: armored cretaceous dinosaur. 265 



mm., and they are all from 5 mm. to 15 mm. in thickness. A 

 single plate is shown natural size in plate LVI, figure 8. 



The lower surface of the ilium is nearly smooth. The only 

 irregularities are the acetabulum and small ridges for muscular 

 attachments. It is gently concave, the concavity becoming 

 stronger towards the outer edge. The acetabulum is in the 

 shape of an elongate oval and is defined by a high ridge of 

 bone. The acetabular cavity is rather shallow and is deeper 

 anteriorly than posteriorly. Its length is 190 mm. and the 

 width, as preserved, is 82 mm. It may have had a somewhat 

 greater width, but not to exceed 90 mm. at the most. The 

 entire ilium measures 48I/2 inches in total length, IOV2 inches 

 at the widest part, and 8 1/2 inches near the middle of the bone. 



The ilium must have had a horizontal position during life, 

 for the position of the acetabulum is such that the femur could 

 not have articulated in it had the bone been in any other 

 position. This condition is not exceptional among dinosaurs, 

 since the ilia of Polacanthus had a similar position and the 

 ilia of Triceratops are horizontal to a much less extent. The 

 articular surfaces for the pubes and ischia have been broken 

 away and lost, so it is impossible to determine the relations 

 of these elements. However, they must have had much the 

 same relations as Seeley (13), Lydekker (17) and Hulke (1j^) 

 have described for Polacanthus. 



The puhes (plate LYIII, figures 1 and 2) are both repre- 

 sented, the right one nearly complete but lacking the entire 

 post-pubic process. This element resembles more nearly that 

 of Claosaurus (15) than it does that of its nearest allies, 

 Polacanthus (13) and Stegosaurus (16). In form the bone is 

 elongate, flattened and spatulate. It curves gently inwards 

 and is only slightly twisted. In thickness the pubis is nearly 

 uniform, becoming thickened proximally to support the pec- 

 tineal process (ectopubis of Baur). The pubis measures 300 

 mm. exclusive of the pectineal process, which is 57 mm. in 

 length. In width the bone measures 112 mm. at the widest 

 part and 86 mm. at the distal end. The external surface of 

 the pubis is crossed by a diagonal ridge for muscular attach- 

 ments. The post-pubis is not represented in the collection 

 save by a fragment which may represent the disal end. The 

 place where the process has been broken from the pubis is 

 large, so th6 post-pubis may have been of some extent. 



