198 Systematic Paleontology 



are too long when added together, though, in other proportions, rela- 

 tively correct. Viewed proximally, the bone is wider than in Moro- 

 saurus, the articular face being more L-shaped, while the angles are less 

 acute in keeping with the more rectangular character of the distal end 

 'of the humerus. Distally, the ulna shows the same sub-rectangular 

 form, as compared with that of Morosaurus. 



Length of ulna estimated 320 mm. 



Width of proximal end 97 mm. 



Depth of proximal end 63 mm. 



Width of mid shaft 33 mm. 



Width of distal end 69 mm. 



IsTo trace of the carpals has been recognized. 



The metacarpals (pi. xvii, fig. 1) are long and slender, but the structure 

 of the hand is as yet unknown, except that it seems to have been much 

 longer relatively than in Marsh's restorations of the fore and hind limbs 

 of Morosaurus grandis.^ 



Pelvis. — There are no bone fragments which can, with any degree 

 of assurance, be referred either to the ilium or pubis. There is, however, 

 the proximal portion of a bone (ISTo. 5677, U. S. National Museum) 

 which Professor Marsh identified with the ischinim. It is much too 

 large, proportionately, to go with the remainder of the skeleton we have 

 been describing, as it approximates that of the young Morosaurus lentus, 

 an individual at least half again as large as the average Pleurocoelus 

 nanus. The bone is also much thicker and differs in its curvature; nor 

 is there any indication of the rotation of the distal end of the ischium 

 upon the long axis of the bone as in Morosaurus. The bone is, however, 

 too defective for a fair comparison. 



Femur. — This bone is represented by the perfect specimen bearing the 

 number 2263, U. S. ISTational Museum, and other less perfect mate- 

 rial. It differs from that of Morosaurus lentus in being much less robust 

 and in the sharp edge of the ridge on the external face below the great 

 trochanter. The lesser trochanter is also much less pronounced in 

 Pleurocoelus. 



^ Marsh, 16th Ann. Rept. U. S. Geol. Surv., pt. i, 1896, pi. xxxviii. 



