156 



longer and more pointed. The mouth has none of the characteristics 

 of Batrachian larvae ; it is wider, the lips are fleshy, have neither 

 papillae nor horny appendages on the lower lip, nor is there any 

 beak on the upper. One of the most remarkable peculiarities, and 

 which especially attracted the attention of Prof. Agassiz, is the ex- 

 istence at each angle of the mouth of a slender filament resembling 

 that of the Siluroid fishes, and which, when placed beside the body, 

 extends as far backwards as the legs. A series of hollow and in- 

 wardly corrugated teeth exist in the upper jaw as in the adult, but 

 none in the lower. 



The skin, like that of other larvae, is mostly very thin, and of a 

 dark-blue color. The back is covered with a patch of integument 

 differing from that of the rest of the surface, which is thick, of a 

 dark-brown color, and resembling that of the adult. In the older 

 specimens patches of similar skin are seen on the nose and on the 

 backs of the thighs and arms. These patches are the beginnings of 

 the metamorphosis by which the larval integument is changed for that 

 of the adult, and gradually extends over the whole body. 



A series of linear groups of follicles begins at the hinder part of 

 the middle line of the back, extends in a curve downwards on either 

 side, ascends over the arms, and ends in a semicircle between each 

 eye and the middle line of the head. On the back the series is partly 

 double, and there are other groups of them over the shoulders. 



The upper caudal fold of skin begins near the middle of the 

 upper edge of the tail, where it is quite narrow, and continues so to 

 the end. The lower fold is very much the broadest, and instead of 

 ending at the base of the tail, as in other Batrachians, extends as far 

 forward as the middle of the abdomen, having its greatest breadth be- 

 tween the legs. The end of the tail is sharply pointed ; the anus 

 perforates the caudal fold behind the abdomen as in other Batra- 

 chian larvae. 



The cavity of the mouth is large, is quite smooth, has no papillae 

 or palatine folds. In common Batrachians the giU-arches are com- 

 posed of two distinct portions. First, an inner, consisting of a broad 

 plate, on the sides of which are developed parallel rows of closely- 

 attached fringes. Second, on the outer border of the arch and 

 nearest to the respiratory opening, a series of dendritic fringes 

 floating free, which are highly vascular, and which form the chief 

 part of the respiratory surface. In the larva of Dactylethra here 

 described, these last are entirely wanting. There are two outer 

 respiratory openings, one on each side, instead of one on the lefl 

 side, as is usually the case. These openings are in the form of fis- 

 sures instead of tubes. 



