144 University of Kansas Geological Survey. 



faces not conspicuously differentiated, and evidently capable of 

 great dorso- ventral flexibility. The carpus and tarsus in some 

 forms are well developed, with closely interlocking bones ; in 

 others the number may be decreased to a single one, a mere 

 nodule set in a broad plate of fibro-cartilage. The metapodials 

 cannot, in many instances, be distinguished from the phalanges, 

 save by their greater size. They are all elongated, hour-glass 

 shaped, somewhat flattened at either extremity, and constricted 

 into a cylindrical or flattened shaft. In Tylosaurus , the thin 

 membrane supporting the digits has been found quite to the ex- 

 tremity and there can be no question but that the digits in all 

 were webbed throughout. 



Scapula. 



CUdastes velox. The scapula is a thin flattened bone, with 

 the lower portion thickened and stout. Its superior border is 

 long and thin, somewhat thicker on the posterior half. The 

 margin is squarely truncated for the attachment of a plate of 

 cartilage, which extends up on the sides of the thorax, as in re- 

 cent lizards. This cartilage is often preserved in a semiossified 

 condition. The convexity is greatest near the middle of the 

 superior border and near the anterior end — the margins more 

 nearly straight between these points. Posteriorly the angle is 

 acute, whence the posterior border, reaching nearly midway to 

 the glenoid articulation, is straight, thinned, and nearly verti- 

 cal, ending in a thin angle. Below this angle the border is 

 concave, rounded and thickened below. The anterior inferior 

 angle is nearly rectangular, the border below in front of the 

 coracoid thin and sharp and concave, ending in a thickened, 

 triangular, much-roughened process, just in front of the cora- 

 coid union, looking downward, for ligamentous attachment. 

 The head of the bone is divided by an oblique ridge into un- 

 equal facets, meeting each other in an obtuse angle. The an- 

 terior one, the larger, is roughened for union with the coracoid. 

 The posterior one is smooth, concave in front, convex behind, 

 looking downward, backward, and outward. The outer surface 

 of the bone is nearly flat, the inner more concave, the head be- 

 ing formed chiefly at the expense of this side. The glenoid 



