120 REPORT— 1839. 



In. LineJf. 



The length of the coracoid was 4 5 



The breadth 3 



The length of the humerus of the same specimen 3 10 



Its breadth at the distal end 3 



The humerus is characterized by the superior length of its 

 shaft, and the sudden hammer-like expansion of its distal arti- 

 cular extremit}'^, which, however, presents the usual flattened 

 shape. The anterior or sternal surface of the humerus is pro- 

 duced into a strong angular process ; its dorsal surface is nearly 

 flat. The radial condyle is most produced, and the breadth of 

 the radius equals nearly the transverse diameter of two of the 

 bodies of the parallel vertebrae of the spinal column. The ulna, 

 and the rest of the bones of the extremity, bear the same large 

 proportional size. In the Ich. iilatyodon the breadth of the 

 radius hardly equals the transverse diameter of a single parallel 

 vertebra. In the Ich. communis and Ich. inter medius the 

 breadth of the radius is less by one third than the transverse 

 diameter of a vertebra from the corresponding part of the body. 

 There is a small notch between the radius and ulna, at their 

 proximal end, in the Ich. tenuirostris. 



It is the large size of the two antibrachial bones, and especi- 

 ally the radius, that renders necessary the hammer-like exten- 

 sion of the anterior condyle of the humerus. In a specimen of 

 Ich. tenuirostris from the Grafton Quarry lias near Warwick, 

 at present in the museum of the Philosophical Institution of 

 Birmingham, the radius and ulna are anchylosed together, and 

 to the humerus. The specimen described by Prof. Jager seems 

 to present the same condition. The radius is distinguished, like 

 that of the Ich. platyodon, by an emargination at the middle of 

 its anterior edge. 



The manus commences by three transversely oval carpal bones, 

 and includes only four digital series of ossicles, which present 

 a moi'e rounded figure than in the previously described species, 

 but resemble most in this respect the paddle-bones of the Ich. 

 platyodon. The radial bone of the first or carpal series is 

 notched anteriorly like the radius itself, but this character is 

 not marked in the next bone below, as in the Ich. platyodon : 

 the radial finger is not bifurcated. 



In the hinder extremity of the Ich. tenuirostris the femur, 

 like the humerus, has a longer shaft than usual, and also a 

 greater transverse extension of its inferior condyles. The tibia, 

 like the radius, is notched at its anterior edge, but the emargina- 

 tion is relatively wider and shallower, and notched also in a 

 slight degree in the corresponding ossicle of the tarsal series. 



The ossicle which is wedged into the interspace between the 

 tibia and fibula is relatively smaller than the corresponding bone 

 in the other Ichthyosauri ; it seems, therefore^ rather to form a 



