404 STRUCTURE AND CLASSIFICATION OF BIRDS 



the table on p. 415. The gall bladder appears to be always 

 present. 



The tensores patagii of Fregata 1 are somewhat compli- 

 cated. The tensor muscle gives off two tendons, of which 

 the anterior, the longus, is much the thickest. The latter 

 is reinforced by an elastic slip from the deltoid ridge of the 

 humerus, whereupon it again divides into two, a branch 

 going to fuse with the brevis ; where this branch joins the 

 brevis tendon that tendon gives off a wristward slip, and is 

 itself continued over on to the ulnar side of the fore arm. 

 There is a patagial fan and a bony nodule where it arises 

 from the junction of the wristward slip of the brevis and the 

 extensor metacarpi radialis. 



In Sula bassana the tendons of the brevis are two from 

 the very first ; the anterior one corresponds to the wristward 

 slip of Fregata, and from it springs the patagial fan. 



The other genera are not very different, save that in none 

 is there an osseous nodule, and that all have a patagial fan. 



The pectoralis I. is double in Fregata, Plotus, Pelecanus, 

 and Sula, variable in Phaeton, single in Plialacrocorax. 



The biceps slip has been occasionally overlooked. It is 

 present in Plotus, Plialacrocorax,' 1 Phaeton, and Sula. 3 It is 

 absent in Pelecanus, Fregata. 



Where present, however, it is slender, and is attached 

 sometimes to the tensor longus, as ordinarily, and sometimes 

 to the patagium itself, as in Colymbus, Podica, &c. The 

 deltoid has the scapular slip in Plialacrocorax. 



The expansor secundariorum has been commonly said to 

 be absent from the wing of the steganopods. This is not, 

 however, at least according to FURBRINGER, an accurate 

 statement of the case. In an embryo of Plialacrocorax 

 carbo unmistakable traces of it were discovered, while in 



287 ; G. L. DUVEENOY, ' Sur la Poche Mandibulaire du Pelican,' Mem. I'lnst. iii. 

 1835, p. 219. 



1 The anatomy of this genus has been described by BUKTOX in Linn. Trans. 



vol. xiii. p. 1. 



2 Not always. FORBES records its absence in P. br.asilicnsis. I did not find 

 one in P. africanus. 



3 Not always ; it is absent in S.fnsca (fide GAEI;<>]>). 



