NO. 1666. OSTEOLOGY OF CAMPT08AURUS—0ILM0RE. 251 



part of the radius (see fig. 41). The articular ends of this bone are 

 smoother than the corresponding parts of the humerus. 



Measuremcrit.t of Specimen, Cat. No. .i282, U.S.N.M. 



mm. 

 Greatest leugth of left ulna 262 



Greatest width proximal end of ulna 75 



Greatest width distal end of ulna 62 



Radius. — The radius is more slender and somewhat shorter than 

 the ulna. It is slightly expanded at the extremities, more especially 

 the proximal end (see /Y^ fig. 27). In cross section the shaft is sub- 

 circular and continues so for most of its length. On the distal exter- 

 nal surface of the bone is a longitudinal groove which receives the 

 roughened border of the distal end of the ulna when articulated. 

 Viewed from the distal end the extremity is heavy and roughly sub- 

 crescentic in outline, with an oblique end, the surface of which looks 

 downward and outward and fits closely to the reverse bevel of the 

 radiale. This is clearly shown in fig. 27, which represents the fore- 

 arm and carpus of the right fore limb of C. hrowni. Cat. No. 4282, 

 U.S.N.M. 



Measurements of Specimen, Cat. No. .'f282, U.S.N.M. 



mm. 



Greatest length of left radius 232 



Greatest width of proximal eiad 58 



Greatest width of distal end 41 



THE FORE FOOT. 



In Camptosaurvs there are five digits in the manus, suj^ported by 

 eight carpalia. The carpus has a simple arrangement, that is, a prox- 

 imal row of three bones — the radiale, intermedium, and ulnare — and 

 a distal row of five. The number of phalanges, beginning with the 

 first digit or pollex, as correctly determined by Marsh, is 2, 3, 3, 3, 2. 



The detailed description to follow is based uj^on a fore foot of 

 Gamptosaurus dispar., Cat. No. 4277, U.S.N.M., from quarry 13, 

 near Como, Albany County, Wyoming. The foot is complete with 

 the exception of phalanges one and two of Digit I, and two and three 

 of Digit IV. The missing parts, with the exception of the ungual 

 of Digit I, which is unknown, will be described from other feet in 

 the National Museum. This foot was found articulated in the field 

 and was so received in the laboratory, and on that account there can 

 be no question regarding the relative position of its elements. The 

 form and proportions of the various bones of the manus are well 

 shown in fig. 28. 



The carpus. — In the carpus of the typical specimen of Campto- 

 saurus dispar.^ No. 1877, Yale Museum, Marsh recogiiized nine carpal 

 bones, but I am unable to- detect more than eight. Specimens in the 



