302 



PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



Although there is a considerable disparity in length between the 

 fore and hind limbs, there appears to be some evidence to show that 

 the bipedal mode of progression was not habitual. While I do not 

 wish to be understood as believing that the upright position was not 

 frequently assumed, still it appears to me that the quadrupedal posture 

 was used more frequently than has been generally supposed. This 

 is shown by the compact, ossified carpus, with smooth, well-defined 

 articulating surfaces, which is supported by comparatively short and 

 stout metacarpals, Avhose function was that of support rather than 

 prehension. "WHien compared with those of animals whose mode of 

 progression is normally bipedal, the suggestion advanced here be- 

 comes more apparent. Trachodon has slender, elongated metacarpals 

 and imperfectly ossified carpus, and Iguanodori also has a tendency 

 toward the lengthening of the metacarpals, though not so marked as 

 in the former genus. The curved femur is also indicative of a flexed 

 limb, which Avould have equalized somewhat the difference in length 

 between the fore and hind legs. This character of the femur is in 

 striking contrast to the straight femur of both Iguanodon and 

 Trachodon^ a provision, as in the Proboscida^, for the support of 

 great weight. The obliquity of the anterior caudal centra indicates 

 a rapid dropping of the tail as it leaves the sacrum, which is also 

 suggestive of a normal quadrupedal position. In the two genera 

 mentioned above the caudals extend straight out from the sacrum 

 without appreciable ventral deflection. 



Through the courtesy of Dr. W. D. Matthew, of the American 

 Museum of Natural History, I am enabled to present in Plate 19 

 the first skeleton of Camptosauims to be mounted, which gives a truer 

 conception of the animal than is obtained from the earlier recon- 

 structions. As seen in the figure, the head is comparatively small, 

 being carried on a gracefully curved neck of moderate length. The 

 thoracic region, which has been given IG dorsals, is of moderate 

 length, borne on stout, clawed limbs, of which the hinder are longer 

 and stouter than the fore. In life this animal was evidently strong 

 and agile in movement. The tail was long, nearly equaling half the 

 total length of the skeleton, and in life it probably served as a bal- 

 ancing organ when the upright bipedal posture was assumed. 



Unlike many of the other predentate dinosaurs, there have been no 

 dermal scutes nor ossicles found, so we have no knowledge as to the 

 dermal covering. 



