1896.] 



ANATOMY OF BUXKOHOrS. 



301 



Rhynclwps shows a peculiar feature of Larus argentatm (c/. fig. 2) 

 and of most Aulis iu tlie existence of tliese patagial tendons (A) 

 on the ulnar side of the arm. In lihynchops there are two instead 

 of only one of these ; they run side by side obliquely, or really at 

 right angles to the loiigijus tendon when the wing is extended, a,nd 

 end upon the extensor metacarjn radialis muscle, on the inner side 

 of the forearm ; the posterior of the two is inserted at a point 



Patagial tendons of Larits argeniaius (after a MS. sketch by the late 

 W. A. Forbes). 



n, osseous nodule. Other lettering as in fig. 1. 



almost exactly corresponding with the insertion of the wristward 

 slip of the hrevis, though, as already said, on the opposite side of 

 the arm. On the opposite wing I could find only a single tendon ; 

 it was, however, very much longer, reaching further over the arm. 

 The pectoralis muscle sends a slip to the patagial tendons, which is 

 slightly differentiated from the rest of the pectoralis as a muscular 

 belly ; there is also a yellowish fibroid slip from the deltoid crest of 

 the humerus. 



I could detect no biceps slip to the patagium on either wing. I 

 looked, of course, very carefully for this muscle, as it is present in 

 all the immediate allies of Rhyncliops. 



The biceps is a very slender muscle which arises from the 

 coracoid only. I found no trace of the missing humeral head. 

 The muscle is divisible into two halves, the division commencing 

 early in the slender tendon of origin. The outer of the two 



