108 BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



i 



the pubes is also unusual, as is the inward curvature of these processes where they 

 are in contact on the median line, as shown in figure 2, plate 21. 



• Seen from the front the cojoined pubes form a V-shaped orifice instead of the 

 Y-shaped opening of most other carnivorous forms. The union of the shafts of the 

 pubes may have extended more proximally than is shown in figure 2, plate 21, for 

 the damaged condition of this portion of these bones makes the exact condition 

 somewhat uncertain. 



There appears to be no median aperture between these bones above the distal 

 triangular foot-like extremity as found in Antrodemus, but again crushing has 

 somewhat obscured the precise condition. 



The distal extremity is missing, but in the restored skeleton has been modeled 

 after Antrodemus. Whether this portion of these bones was present when the 

 drawing of the pelvis (see fig. 63, also pi. 23) was made under Professor Marsh's 

 direction is not known. 



Measurements of pubis of Ceratosaurus nasicornis Marsh. 



mm. 



Greatest length. . . , , 670 



Greatest transverse diameter, proximal end (right), 130 



Greatest transverse diameter at center of combined shafts 120 



Greatest width of pubic orifice 150 



Ischium- (is.). — The ischia of Ceratosaurus are comparatively slender, project'- 

 downward, and well backward in the articulated pelvis. The distal three-fourths of 

 their length are in close apposition and firmly coossified. There is no distinct 

 obturator process present, as in Antrodemus. The pubic process of the ischium is 

 much wider dorsoventrally than the corresponding process in Antrodemus. The 

 ventral part of this process, like the ischiac process of the pubes, turns inward and 

 meets its fellow on the median line, thus completing the boundary of the posterior 

 part of the U-shaped pelvic orifice. 



The distal ends of the ischia are missing, and as with the pubes one can not be 

 certain that Marsh had them when drawings for figure 63 and plate 23 were prepared. 

 The bone, however, does show that there was an abrupt forward expansion of the 

 enlarged distal end but as to its extent or shape there is no clue in the type specimen. 



Measurements of ischium of Ceratosaurus nasicornis Marsh. 



mm. 



Greatest length of ischia, from middle of acetabular border to distal end, estimated 505 



Greatest diameter of proximal end 160 



Least diameter of shaft 27 



HIND LIMB AND FOOT. 



Femur.— The femur of Ceratosaurus is so like that of Antrodemus as to be 

 almost indistinguishable. It is longer than the tibia, has the same curvature of the 

 shaft, and practically the same position of the trochanters and roughened areas for 

 muscular attachment. Crushing has somewhat altered certain portions of the bone, 

 so that in comparing it certain differences observed disappear when this factor is 

 taken into consideration. Its smaller size relatively smaller fourth trochanter and 

 shorter lesser trochanter constitute the chief features for distinguishing it from, the 

 femur of Antrodemus. 



