308 NOTES ON THE ANATOMY 03? BIRDS, 



origin to insertion; again in other cases (e.g., Anatidce and Gruidae), 

 one of the terminal tendons is inserted into the head of the radius 

 and the other bifurcates to become attached to both radius and 

 ulna. 



A further peculiarity of this muscle in the Columlidm is that 



it gives off a broad quadrilateral offset to aid in the extension of 



the anterior alar fold. A vermiform muscle with a similar 

 function and more intimately related to the biceps is to be found 



in most, if not all, Waders, and many Natatores (PJialacrocorax, 



Larus, Anatidce), but Didanculus strigirostris is the only bird that 



resembles the Columbidce in the flat expanded form of this tensor 



accessorius as it may conveniently be designated. 



4. — The tensor membranes anterior is alae consists of two separate 

 muscles — the tensor longus and tensor brevis. The tensor longus has 

 two distinct separate heads of origin ; the one consists of a broad 

 and flat fleshy belly, which takes origin from the approximated 

 ends of the coracoid, scapula and clavicle, — chiefly from the 

 coracoid — and arches over the shoulder- joint after the manner 

 of the deltoid of mammals (to part of which muscle in fact it 

 corresponds); distally it gives origin to the " elastic tendon" 

 of the anterior alar fold ; the other part of the muscle takes the 

 form of a small cone-shaped prolongation of the peetoralis major. 

 The tensor brevis may be described also as a small conical offset 

 from the peetoralis major ; it is however firmly connected with the 

 pectoral ridge of the humerus. In some birds (e.g. Larus, 

 Brucliigavia) the tensor brevis is rejoresented only by a fasciculus 

 of yellow elastic tissue ; in others it is altogether absent. In the 

 Psittacidce again the tensor longus is not independent of the 

 peetoralis major, and its tendon is connected by elastic fibres with 

 the cervical muscles. 



5. — The extensor carpi radialis longior and the extensor meta carpi 

 radialis are so intimately blended as virtually to form one muscle. 

 This is not an uncommon arrangement, being characteristic of 



