104 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



Fig. 60.— Left radius, ulna and fore foot of CERA- 

 TOSAURUS NASICORNIS MARSH. No. 4735, U.S.N. M. 



Type— \ nat. size. R , radius; U, Ulna, I, II, III, 



and IV, METACARPALS ONE TO FOUR. SHOWN AS 

 FOUND IN THE MATRIX, SEVERAL OF THE BONES NOT 

 ENTIRELY UNCOVERED. 



Comparative measurements of radii, Ceratosaurus and 

 i Antrodemus. 



Antrodemus 



valens, 



No. 4734, 



U.S.N.M. 



Greatest length of radius 



Greatest transverse diameter of 



proximal end 



Greatest transverse diameter of 



distal end 



222 

 56 

 40 



Forefoot. — As mentioned above a complete 

 fore foot of Ceratosaurus is as yet unknown, 

 though the articulated left manus gives a f airly 

 good idea of its structure. The phalangial 

 formula, however, remains to be definitely 

 determined. With the type the following 

 bones of the fore feet . are preserved : Meta- 

 carpals I, II, III, IV, and proximal phalanges 

 of digits 2, 3, and 4 of the left manus; meta- 

 carpals IV, distal halves of metacarpals I and 

 II, and proximal phalanx of digit 2 of the 

 right foot. 



Carpus. — Ossified carpal bones are unknown 

 in Ceratosaurus, and although the articulated 

 foot mentioned above was found in position 

 in relation to the distal ends of the radius 

 and ulua (fig. 60), no carpal ossifications 

 were found in the intervening matrix. This 

 would appear to indicate an unossified carpus, 

 for this specimen is an old individual, as 

 clearly demonstrated by the coossified pelvic 

 and metatarsal bones. 



Metacarpus. — The metacarpus consists of 

 four bones, as shown by the foot found in 

 place as depicted in figure 60. The two me- 

 dian metacarpals are moderately robust ele- 

 ments, but I and IV are much reduced. 



Metacarpal I is a short bone with slightly 



expanded proximal and distal ends. The dis- 

 tal end is deeply grooved and turns inward away from the central axis of the 

 foot as in most other Theropod dinosaurs. This diversion is due to the unequal 

 development of the articulating facets, the outer one being the larger and extending 

 farther forward, as in Gorgosaurus. It is unlike Antrodemus in this respect, where 

 a bend in the shaft diverts it inward. Both facets on this end curve down and 



