OSTEOLOGY OF CARNIVOROUS DINOSAURS. 135 



seventh chevrons are present (pi. 35, fig. 1). The articular end bridges across the 

 haemal arch in all those preserved. 



Pelvis.— The pelvic bones are firmly coossified with each other, as in Ceratosau- 

 rus nasicornis Marsh from the Morrison beds — a condition that also prevails in the 

 Belly River Ornithomimus altus. 



The postacetabular portion is especially thin, elongated, and terminates in an 

 abruptly truncated end which is without thickening of the border. On the internal 

 side there is the usual shelf of bone that extends inward and backward from the 

 ischiac peduncle (fig. 67) to join with the sacral ribs of sacrals 3 and 4. 



Viewed from above the articulated ilia lap closely along either side of the 

 spinous processes of sacrals 1 and part way on that of sacral 2, at which point they 

 begin to diverge until their upper posterior borders are 110 mm. distant from one 

 another. The postacetabular portion of the ilium at the end is 115 mm. deep. 

 The bone as preserved in this specimen has a greatest length of 420 mm. It is esti- 

 mated that the total length would be about 520 mm. The preacetabular portion 

 has a greatest vertical width at broken end of 150 mm. The acetabulum measures 

 97 mm. antero-posteriorly and 81 mm. dorsoventrially. 



Pubes. — The head of the right pubis is firmly coossified with the ilium and 

 ischium and is all that remains of this pair of bones. This head has a greatest 

 width of 125 mm., subdivided as follows: 82 mm. represents the part joining the 

 public peduncle, while 43 mm. represents its contribution to the boundary of the 

 acetabulum. Viewed laterally the pubic peduncle and pubis form a much wider 

 plate at their junction than in Ornithomimus altus as figured by Osborn, but I 

 am inclined to think that this portion is missing in the restored skeleton, as 

 suggested by the missing centra that pass back of this region, and which are indi- 

 cated by dotted lines only. Compare figure 1, plate 35, with Osborn's figures of 

 the restored skeleton of Struihiomimus altus. 



Ischia. — Both ischia are present, and, with the exception of a small portion 

 missing from their distal ends, are perfectly preserved. The proximal ends have 

 the usually Y-shaped expansion with articular faces that articulate with the ilium 

 and pubis (fig 67, is.). In the articulated pelvis the ischia extend downward and 

 inward to meet on the median line throughout the greater part of their length. 

 This union on the upper two-thirds by their inner edges is on the lower third made 

 very strong by the great anteroposterior expansion of their distal ends, which are 

 closely applied on the median line. A short aperture (o, fig. 67) passes between 

 the bones immediately above the expanded distal ends. 



ORNITHOMIMUS TENUIS Marsh, 1890. 



Ornithomimus tenuis Marsh, Amer. Journ. Sci., ser. 3, vol. 39, p. 85, 1890. — Hay, 0. P., U. S. 



Geol. Surv. Bull. 179, p. 494, 1901. — Osborn, H. F., Contributions to Canadian Paleontology, 



vol. 3, pt. 3, p. 13, 1901.— Hatcher, J. B., Science, new. ser., vol. 16, No. 412. p. 831, 1902; 



U. S. Geol. Surv. Bull. 257, p. 87, 1905.— Bowen, C. f), U. S. Geol. Surv., Professional Paper 



90-1, p. 132, 1915. 

 Struihiomimus tenuis Osborn, H. F., Amer. Mus. Nat. Hist. Bull., vol. 35, pp. 740, 741, 1917. 



Type.— No. 5814, U.S.N.M., consists of the distal half of metatarsal III, of 

 the left foot. Collected by J. B. Hatcher, 1888. 



