NO. 1878. MOUNTED SKELETONS OF CAMPTOSAURUS—GILMORE. 689 



whose function was that of support rather than of a grasping or pre- 

 hensile organ. 



As stated previously, while the wi-iter believes that the upright 

 bipedal posture was frequently assumed, it does appear from the 

 facts mentioned above that Canvptosaurus used the quadrupedal 

 mode of progression more frequently than any other known member 

 of the Ornithopoda, and in tliis genus it may represent the beginning 

 of the development of a fore foot where quadrupedahsm was to 

 become a fixed means of locomotion as it has in Stegosaurus and in 

 the Ceratopsia. 



The stiff divergent pollex, brought about by the ankylosis of the 

 first metacarpal (which is much shortened) with the radiale, is an 

 interesting feature of the fore foot. In this respect there seems to be 

 a trend toward the development of a "spikelike" 

 digit as found in the fore foot of the Iguanodon 

 of Europe. (Compare figs. 1 and 2.) The skull 

 has been modeled after a careful study of all 

 known cranial material, and it is believed to be 

 the most correct restoration yet produced, 

 although future discoveries will probably show 

 the present conception to be in error in some 

 particulars. 



In Camytosaurus the dentition is confined to 

 the rear portions of the jaws, the anterior part 

 of the mouth being toothless and probably 

 sheathed in a horny beak which served for 

 cropping oft' the bushes or herbage on which 

 these animals fed. The teeth are of moderate 

 size wdth sculptured margins (see fig. 3), im- 

 plying a food of rather yielding character which 

 did not require forcible mastication. 



These skeletons represent the animals as touchmg nearly the whole 

 length of the toes (excepting the first) to the ground. They were 

 so mounted because of the fact that all the three-toed supposed dino- 

 saurian footprints show the imprint of nearly the full length of the 

 phalanges. 



The pathological condition of the right ilium of C. Irowni is of mter- 

 est in shomng to what extent the shape of a bone may be modified 

 by external mjury (see pi. 58). On the posterior haK, the comparatively 

 thin, platelike part of the ihum is divided vertically, the two halves 

 sweUing out to form the walls of a cavity which extends downward, 

 emerging on the ventral border. The cavity is longer than wide, 

 measuring on the upper border of the opening 86 mm. in a longitudi- 

 nal direction and 46 mm. in the transverse, the ventral exit bemg 

 94428°— Pros.N.M.vol.41— 11 44 



Fig. 2.— Left fore foot of 

 Iguanodon. I, first digit 



OR POLLEX. 



