170 THE VOYAGE OF H.M.S. CHALLENGER. 



from a comparative point of view, are of but little value. The descriptions indeed of all 

 the authors mentioned, are so meagre and unsatisfactory, that I have felt justified in 

 giving a more minute account of these organs than would otherwise have been 



Do O 



necessary. For the sake of accurate comparison. I have selected Eudyptes ckrysocome 

 from Tristan d'Acunha as a type, and having in the first place described at length each 

 portion of the alimentary canal of that bird, I have thereafter added comparative remarks 

 on the anatomy of the other species which I have dissected. 



The Mouth. 



The tongue of Eudyptes chrysocome from Tristan d'Acunha, is elongated and some- 

 what rounded at its free extremity. It measures Ifth inches in length and fths of an 

 inch in greatest breadth. Its upper surface is covered by a series of stout conical 

 papillae, the free extremities of which are directed backwards towards the throat. The 

 papillae are arranged in nine longitudinal rows, one of which occupies the middle line 

 of the tongue, while four others are arranged symmetrically on either side of the 

 middle line. The papillae composing the central rows are of larger size than those 

 situated externally. The latter diminish in size from the middle line to the lateral 

 margins of the tongue. The base of the tongue is separated from the rest of the organ 

 by a groove, which is most clearly defined when the point of the tongue is depressed. 

 The basal portion so separated is triangular in form, the apex of the triangle being 

 directed forwards. It, like the rest of the organ, is invested by recurved papillae. 



The superior laryngeal aperture is placed immediately behind the root of the tongue, 

 and presents the form of an elongated slit, bounded on either side by an elevated portion of 

 the mucous membrane, which, for convenience of description, may be named the " laryngeal 

 pads." These pads (PI. XIII. fig. 1) together are of an oval form, and measure fths of an 

 inch in length, and ^ an inch in greatest breadth. They are slightly raised above the level 

 of the adjacent mucous membrane. Like the tongue, they are covered with conical recurved 

 papillae, which, however, are of smaller size and more sparsely and irregularly distributed 

 than on the dorsum linguae. The papillae are of larger size at the margins of the laryn- 

 geal slit than at the external margins of the pads. The laryngeal aperture has the form 

 of an elongated slit, which at first sight apparently corresponds in length to that of the 

 laryngeal pads. Upon closer examination, however, the aperture is seen to correspond 

 only to the anterior half of the antero-posterior diameter of the pads, the posterior 

 segment of the apparent aperture being merely a superficial groove between the pads of 

 opposite sides. To their outer side the mucous membrane of the mouth is smooth and 

 devoid of papillae, presenting only the apertures of several buccal glands, the ducts of 

 which open into the mouth in this region. 



The floor of the mouth below the tongue is formed by a triangular portion of mucous 



