388 ON THE PETRELS COLLECTED DURING 



The liver is usually about equilobed, the lobes not being large, and 

 rather triangular in shape. In the Albatrosses, however, the right lobe 

 becomes elongated and distinctly bigger. The gall-bladder, developed on 

 the right hepatic duct, is always present so far as my observations 

 extend. The hepatic ducts (PL XIV. fig. 1, rji.d., l.h.d.) open close 

 together into the ascending arm of the duodenal loop, close to the 

 pancreatic ones, of which there are usually two or three in Majaqueus. 

 In the specimen of Tkalassceca glacialoides dissected the left hepatic duct 

 divided, soon after leaving the liver, into two branches, each of which 

 opened separately into the duodenum, so that altogether this received 

 three ducts from the liver. The vitelline rudiment is not to be found in 

 the adult birds. The bursa fabricii, in young birds at least, is a well- 

 developed large sac, with thick glandular walls, and a small opening into 

 the cloaca. The spleen is circular, or nearly so. 



3. Myology. 



The myology of the Tubinares presents many features of interest, as 



will be seen from the following description. The species of the group, 



Zool. Chall. broadly speaking, resemble each other very much in the details of their 



Exp.vol.iv. muscular structure, though in the fore limb the structure of the biceps 



and the termination of the tensor patagii tendons, and in the hind limb 



the presence or absence of the ambiens and the accessories to the femoro- 



caudal and semi-tendinosus, present characters available for taxonomie 



purposes. 



Anterior Extremity. 



Pectoralis primus. This muscle is always largely developed in the 

 Tubinares, as might have been expected from their great powers of flight. 

 It is peculiar in that it is always easily divisible into two quite separate 

 layers superimposed on each other, besides which it gives off thin fan- 

 like cutaneous branches. A similar disposition of the pectoralis primus 

 in two distinct layers is very characteristic of many of the Ciconiiform 

 birds of Garrod, occurring in all the Storks and CathartidsB, and in 

 Phaethon, Freyata, Plotus, Sula, and Pelecanus amongst the Steganopodes. 

 A tendency to a similar condition, though the two layers are only 

 separable with difficulty, may be seen in the Ardeidse, Falconidae, and 

 Scopus. 



The superficial layer of the pectoralis primus arises (vide PI. XVI. figs. 1 

 and 2, p. la) from the posterior and lateral margins of the body of the 

 sternum, from the margin of the sternal carina, and from the inferior 

 border and external surface of the clavicles. In the latter position it is 

 divisible into two layers, one arising from the extreme margin, the other 

 And deeper from the surface, of those bones. The common insertion into 

 the large humeral crest is very tendinous behind, more fleshy anteriorly, 



