Tlie Food of Fresh- Wafer Fishes. 465 



This fish depends, therefore, entirely upon the very remarkable 

 straining apparatus borne by the gills, the immense oral open- 

 ing, and the equally free provison for the exit of water from 

 the gill chamber, enabling it to pass vast quantities of water 

 through its branchial apparatus. The gills are very elongate, 

 each having the form, when the mouth is closed, of a slender U 

 with the sides parallel and closely approxiuiated, the lower arm, 

 however, extending somewhat further forward than the upper. 

 Each gill bears throughout its whole length a double series of 

 very long, fine, numerous, and slender rakers, the two rows 

 separated by a membranous partition borne upon the anterior 

 surface of the arch, — this partition a little higher than the rows 

 of rakers, and slightly thickened on the internal edge, so as to 

 enclose the tips of the rakers when the parts of the apparatus 

 are approximated. These rakers average fully twice the length 

 of the corresponding gill filaments, and numbered, on the first 

 gill of a specimen about one and a half feet long, five hundred 

 and sixty rakers in the anterior series. A half row of similar 

 rakers is borne by the fifth branchial arch, corresponding to 

 the inferior pharyngeal bones of most fishes. The individual 

 rakers are toothless, smooth, cartilaginous, and nearly naked, 

 the filaments covered by a thin epithelium, thickened at the tip. 

 Interlocking as these do when the branchial apparatus is ex- 

 tended, they form a strainer, sufficient to arrest the smallest liv- 

 ing forms above the Protozoa. There are no pharyngeal jaws 

 or teeth, nor is there any apparatus of mastication elsewhere. 



In the absence of any raptatorial teeth or crushing appa- 

 ratus in its large and feeble jaws or in its throat, it is certain 

 that this species cannot feed upon fishes or mollusks ; and 

 the character of the intestine makes it very probable that it 

 never purposely swallows mud or takes a large percentage of 

 vegetable food. On the other hand, its enormous mouth, and 

 the remarkable straining apparatus in its branchial cavity give 

 it access to the immense stores of minute insect and crustacean 

 life most commonly reserved for young fishes ; while its struc- 

 tures are likewise evidently adapted to the larger soft-bodied 

 insects and insect larva). 



The use of the paddle-like snout is as yet a matter of con- 

 jecture, slightly assisted, perhaps, by a knowledge of the princi- 



