AND AVES OF NORTH AMERICA. 



219 



adhering to the matrix on the body of the same vertebra. That of the seventh is wider 

 than that of any of the dorsals, but is compressed like those preceding. The length of 

 the shaft is nearly equal to that of the centra of the 6th, 7th, and 8th vertebrae, the two 

 being proportioned as 17 to 20. 



The heads of the dorsals area slight kidney-shaped oval, with a shallow median con- 

 cavity. On the tenth vertebra, tin; bead is much shortened and concave medially, on the 

 posterior face. The concavity is posterior on several vertebrre in advance of tins point. 

 The form of the shaft of the ribs is proximally, broad above, and narrowed below, i. e. 

 concave wedge-shaped in section. The superior face turns over to the posterior, and is 

 lost in it, and the shaft becomes cylindric. The distal extremities of the seventh cervical 

 and of two of the dorsals, the only ones preserved, are deeply concave with a sharp edge. 

 The limbs in this genus are of remarkable form. Unfortunately, no metacarpals or 

 phalanges have been preserved. There are the remaining bones of one side and a portion 

 of those of the other. The proximal portion of the left scapular and both coracoids also 

 remain. The right coracoid is crushed and adhering closely to the ninth, tenth and 

 eleventh vertebree, its glenoid cavity apparently in its normal position opposite the middle 

 of the; eleventh. Thus the distance of the limbs from the head is apparently ascertained. 

 The external margin of the anterior part of tbis element is parallel to the vertebral axis 

 in place; the posterior corresponding margin much incurved and thinned out to an acute 

 edge. The anterior portion is more prolonged than the posterior, while the inner margin 

 forms a, regular curve without cmarginations. The most extensive articular margin is the 

 inner, with the scapula; it is suture-like, corresponding to a singularly indented margin 

 of the scapula,. Inside of its anterior margin a moderate foramen pierces tin; plate. The 

 lower articular margin is lobed, the posterior lobe being the outline of the glenoid cavity. 

 The greater part of the scapula is lost; it has apparently bad hut little expanse poste- 

 riorly, where the margin is thick and little curved. The anterior part of the plate is thin 

 and much produced, [ suspect into a pro-coracoid or acromial process. It resembles the 

 basis of Cuvier's pubis of Mosasaurus, which bone I suppose to be; the scapula of that 

 genus. In the present animal the anterior margin is strongly incurved and acute, and 

 does not reach the articular face, but bounds a rough triangular projection in front of it. 

 The humerus is a singular bone, and unlike that of any other animal; it approaches 

 nearest that of Sphargis. It is a short, wide, flattened bone, distally as broad as long, 

 proximally a little narrower, contracted medially, with such prominent muscular insertions 

 as to give it four process-like angles in its plane, and two others projecting posteriorly 

 from the head. The articular extremity presents an elongate oval facet for the ulna, and 

 a semi-discoid one for the radius. The radius is, in accordance with this, flat anteriorly 

 and convex posteriorly at its proximal extremity; its shaft is very short, and the distal 



