end is somewhat weathered and worn, and does not show the very rugose nature observed in better preserved specimens. The head is very convex, the portion for cartilaginous attachment extending far around both anteriorly and posteriorly. There is a well developed trochanter on the dorsal surface.
The ulna is a pentagonal block of bone, the proximal being thicker than the distal end. The proximal end is slightly convex and was opposed to the concave
Fig. 8. View of the proximal end of the humerus of Baptanodon natans (No. 1441). One half natural size. d., dorsal surface.
Fig. 9. Ulna of Baptanodon natans (No. 1441). One half natural size. d., distal end ; p., proximal end.
Fig. 10. Radius of Baptanodon natans (No. 1441). One half natural size. d., distal end ; l., lateral border, restored ; p., proximal end.
facet on the distal end of the humerus though probably separated by cartilage. The other sides are slightly convex and were evidently surrounded by a thick cartilage as indicated by their rugose surfaces. The upper and lower surfaces are slightly concave antero-posteriorly. The element appears to be More angular than the ulna of Baptanodon marshi.
Measurements.
No. 1441. Greatest length of ulna antero-posteriorly....................................................................................................................................................................................................................................................40 mm.
" 1441. " breadth of ulna....................................................................................................................................................................................................................................................50 "
" 1441. " thickness of ulna, proximal end....................................................................................................................................................................................................................................................35 "
The radius is a sub-quadrate element somewhat wider than long and like the ulna thicker on the proximal than on the distal end. The external margin is miss-ing but apparently reduced to a comparatively thin edge: The radius is larger than the ulna in all of its dimensions. The proximal end is convex and was opposed to the largest of the three concave facets on the distal end of the humerus. The inner side is slightly convex, the distal flat, and all except the external side are rugose. The upper and lower surfaces are slightly concave antero-posteriorly:
Measurements.
No. 1441. Greatest length of radius antero-posteriorly, estimated....................................................................................................................................................................................................................................................51 mm.
" 1441 " breadth of radius....................................................................................................................................................................................................................................................65 "
" 1441 " thickness of radius, proximal end....................................................................................................................................................................................................................................................42 "
