OSTEOLOGY OF THE AEMOEED DINOSAUBIA. 



113 



Coming to the caudals of the distal portion of the tail, of which there are 10 

 present, these show such distinctive differences from those of the other species, 

 (fig. 67) that the question of their proper association with this specimen was at 

 once raised. In reply to my inquiry, Mr. Eeed assures me that there can be no 

 question but that they belong to the type-specimen, as this skeleton was found 

 isolated, that is, there were no bones of other animals found in the same quarry 

 with it. 



The characters by which these vertebrae differ from those of the other species 

 of Stegosaurus are contrasted in the two parallel colunms below. 



S. longispinus . 



Centra depressed. 



Centra rounded when viewed from end. 



Sides of centra deeply concave. 



Vestigal transverse process. 



Centra mushroom headed. 



Other species. 



Centra compressed laterally. 



Centra hexagonal when viewed from end. 



Sides of centra moderately concave. 



Process wanting. 



Heads of centra without special expansion 



The spinous processes are missing from all of the distal 

 caiidals. Measurements taken of the centra show the trans- 

 verse diameter to always exceed the vertical, whereas in 

 the distal caudals of other species the vertical always equals 

 if it does not exceed the transverse diameter. 



Although there are considerable portions of the sa- 

 crum present it is too fragmentary to be compared to advan- 

 tage. 



Such dorsal vertebrae as are preserved show the usual 

 elongated neural processes, with upwardly directed diapophy- 

 ses, and small laterally compressed centra. These show no 

 distinctive features. 



The cast of the sacral cavity is depressed and consid- 

 erably more expanded laterally than in S. ungulatus. How 

 much of this flattening may be attributed to crushing it is 

 impossible to say. 



The ischia are of the same size as those of S. stenops, and 

 differ only in minor details (pi. 25, fig. 4). 



The femur in its general proportions closely resembles 

 those of the type-specimen of S. stenops (fig. 45), as in that 

 species the femur may be distinguished from those of S. 

 ungulatus by the presence of the finger-like lesser trochanter 

 on the external anterior face of the proximal end (a, fig. 68). 

 The condyles are illy defined, being wide apart, with articular 

 surfaces confined almost exclusively to the distal view. It 

 has a greatest length of 1,082 mm.; other measurements are 

 given in table on page 83. 



The few ribs present show the usual T-shaped cross-section of the" proximal 

 portion. 



Fig. 68.— Right femuk of 

 Stegosaurus longispinus. 

 Type no. D 54, UNrvEKSiTY 

 OF Wyoming, ^nat. size. 

 Front view, a, Lesser 

 trochanter; b, gf.eater 

 trochanter; ft, head. 



