102 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



Ill the mountod skeleton they have been restored, but have been made much 

 too heavy, especially their distal portions, which are probably attenuated as fovmd 

 in Antrodemus. 



Abdominal rihs. — That a cuirass of abdominal ribs was present in the completp 

 Ceratosaurus skeleton is indicated by a few fragmentary rod-like pieces of bone 

 found preserved in a block of sandstone which accompanied the other parts of the 

 type specimen. The determination of the character of these ribs must await the 

 discovery of more complete materials. 



SHOULDER GIRDLE. 



Plates 26 and .30. 



The incomplete left scapula and the fragmentary proximal border of the coossi- 

 fied coracoid is all that is known of the pectoral girdle in Ceratosaurus nasicornis at 

 this tim.e. These bones have suffered considerable crushing, so that a true concept 

 of their original shape and proportions is somewhat difRcult of determination. 

 No traces of the sternal elements have been foimd. 



Elsewhere I have pointed out that this scapula formed the basis for the drawing 

 of the shoulder blade in the so-called fore limb of AUosavrus fragilis as published by 

 Marsh (see fig. 58). The coracoid illustrated in the same fore limb was made from 

 a drawing in Phillips Geology, reduced to the proper proportions, as explauied on 

 page 56 of the present paper. 



Scapula. — The scapula as now preserA-ed (fig. 1, pi. 26) is lacking the distal 

 extremity, so that it is not positively known whether the blade was nonexpanded, 

 as represented by Marsh, or whether it was expanded as in Antrodemus valens. I 

 am inclmed to the opinion that it was expanded somewhat, as shown in the mounted 

 skeleton, plate 30, though as represented there the scapula is probably too short. 



The shaft is relatively thin with a sharp upjier and thickened lower border. 

 The part of the shaft preserved is quite uniform in width, and although pertaining 

 to a considerably smaller individual than the scapula of Antrodemus valens Leidy, 

 Xo. 4734, U.S.X.M., with which I have compared it, the shaft is very much wider, 

 as showTi in the comparative measurements given below. 



A ntrodemus 



valens 



No. 4734, 



U.S.N.M. 



Greatest width of shaft near proximal end 

 Greatest width of shaft near middle end . . . 

 Greatest width of shaft near distal end — 



52 



57 

 64 



e Estimated. 



Longitudinally the scapula is concave on its inner aspect, though doubtless 

 much straightened by crushing. The expanded proximal end, though poorly pre- 

 served, shows this extremity to be much wider (vertically) than the corresponding 

 part of the Antrodemus scapula. The thickened ventral border above the glenoid 

 fossa turns downward with a more decided sweep than it does in the latter genus. 



