22 THE VOYAGE OF H.M.S. CHALLENGEE. 



glacicdis is represented ! ). In the Oceanitidae and Diomedeinae this epithelium is softer ; 

 its character in other Petrels is but an exaggeration or reproduction of that existing in 

 some other birds, particularly that occurring in such storks as Xenorhynchus. 



The displacement of the pyloric orifice of the gizzard to the left necessitates a corre- 

 sponding change in the commencing duodenum, so that this at first ascends in an upward 

 curve towards the right before it returns to form the backwardly-directed loop, character- 

 istic of Aves and Mammalia, round the pancreas (PI. II. fig. 1, p.). 



This peculiar upward curve of the commencing duodenum, the singularly small inverted 

 stomach, and enormously deep proventriculus are all peculiar, so far as I am aware, to the 

 group of Tubinares, though universal amongst them, and no other bird yet examined 

 has, so far as I know, a similar disposition of these viscera. 2 



The intestinal caeca are entirely absent in all the Oceanitidse, but are, with one 

 exception, present, though of small size, in the Procellariidae. They are always short 

 and globular, and closely connected to the intestine, so as to appear as mere nipple- 

 like projections from it. Plate II. fig. 3 represents those of Majaqueus slightly en- 

 larged. They are usually situated quite close to the cloaca, the large intestine in nearly 

 all the Tubinares being quite short ; the length of the caeca themselves rarely 

 exceeds *25 inch, except in the very largest species (vide table, p. 23). In five speci- 

 mens (one a nestling) of Cymochorea leucorrhoa that I have examined, I find only 

 a solitary caecum, lateral in position, developed, owing apparently to the abortion of 

 its fellow. As Mr. Swinhoe in his description of Cymochorea monorhis 3 also records 

 the caecum as single, it is probable that the existence of such a single caecum is 

 a character of the genus Cymochorea. It is not unusual, I may observe, in a group 

 of birds in which the caeca are of small size, and probably of no physiological im- 

 portance, to find specimens or species with the normal number of caeca reduced by 

 one. I may give as instances Mergus albellus (cf. Hunter, Observ., vol. ii. p. 325 ; and 

 Garrod, Coll. Papers, p. 220) amongst the Anseres, and Plotus anhinga (Garrod, I.e., 

 p. 345) amongst the Steganopodes, not to mention all the Ardeidae amongst the 

 Herodiones. In Halocyptena, in the only specimen yet examined, I could find no trace 

 of any caeca at all, so that the tendency to their disappearance already observable in 



1 The figure of Cams and Otto (Tabulaa Anat. Comp. Illustr., part 4, t. vi. figs. 15, 16) of the epithelium of the gizzard 

 of Fidmarus glacicdis does not at all faithfully represent what I have seen in two (quite fresh) specimens of that bird, 

 nor have I ever in other Petrels seen epithelium of such a corneous and pavement-like nature as that figured by them. 

 I have, therefore, had one of my specimens carefully drawn of the natural size. In this place it will be well to recall 

 the still more highly developed gastric epithelium of some of the Fruit-pigeons (Phcenorhina goliath and Carpophaga 

 latrans) described by Verreaux and Des Murs, Viallanes and Garrod (vide antca, Report on the Birds, pp. 152-154). 



2 The description of these parts in the Little Auk (Alca alle) given by Professor Owen (Anat. Vert., vol. ii. p. 163), 

 and originally due to Home (Lect. Comp. Anatomy, i. pp. 283, 284, 1814) does not all apply to that bird (cf. the figure 

 and description given by Macgillivray in Audubon's Ornithogical Biography, iv. pp. 306-309), and probably refers to 

 some member of the Tubinares. 



3 Ibis, 1867, p. 387. I have examined the type of this species, which is now in Mr. Seebohm's collection, and find 

 it to be a true Cymochorea. 



