110 BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



that genus it is separated from the greater trochanter by a wide diagonal intero- 

 external groove. The inner or fourth trochanter is shorter in its longitudinal length 

 and occurs slightly higher proximally on the shaft than in Antrodemus. The princi- 

 pal features of this bone are well shown in figure 64, where it is illustrated in three 

 aspects. 



Measurements of femur of Ceratosaurus nasicornis Marsh. No. 4735, U.S.N. M. 



mm. 



Greatest length '. ! 620 



Greatest diameter of head 150 



Greatest diameter across condyles 135 



Mid diameter of shaft 52 



Tibia (t.). — -The right tibia, and fibula of Ceratosaurus, articulated with the 

 astragalus and calcaneum, all completely preserved, are shown in figure 65. 



As in Antrodemus the tibia is shorter than the femur and with quite similar 

 contours and similar attachments. The greatest observable difference between 

 these two bones is in the greatly reduced size of the cnemial process in the Cera- 

 tosaurus tibia and its relatively narrower shaft when viewed from the front. Com- 

 pare figure 65A with 48A. 



The anteriorly directed process on the proximal end is also longer and extends 

 more directly forward than in Antrodemus, though the latter peculiarity may be 

 partly due to crushing to which this part of the bone has been subjected. The 

 area covered by the ascending process of the astragalus is also restricted as compared 

 with Antrodemus. 



The principal features of this bone are well shown in three aspects in figure 65. 



Measurements of tibia, Ceratosaurus nasicornis Marsh. No. 4735, U.S.N. M. 



mm. 



Greatest length 555 



Greatest diameter of proximal end 180 



Greatest diameter of distal end 140 



Fibula (/.). — Like the tibia, the fibula of Ceratosaurus bears a close resemblance 

 to that of Antrodemus. The greatest dissimilarity is found in the form of the proxi- 

 mal end. When viewed from the side — compare B, figure 65 and B, figure 48 — it 

 will be seen in Ceratosaurus the fore and aft expansion of this end begins much 

 lower down on the shaft, whereas in Antrodemus there is no widening until close to 

 the upper articular end. This end is subcresentic in outline. The distal end when 

 viewed from the side is squarely truncated as compared with the evenly rounded 

 end in Antrodemus. 



Measurements of fibula of Ceratosaurus nasicornis Marsh. No. 4735, U.S.N.M. 



mm. 



Greatest length of fibula 502 



Greatest diameter of proximal end 125 



Greatest diameter of distal end 53 



Least diameter of shaft 28 



Tarsus. — The tarsus of Ceratosaurus so far as known at this time consists of 

 three bony elements; the astragalus and calcaneum forming a proximal row, and 

 a single disk-like tarsale found attached by matrix to the proximal end of meta- 

 tarsal III. There was probably a second tarsale above metatarsal IV, as in Antro- 

 demus, these two forming the distal row of the tarsus. 



