40 Mountain Trout of Kemaon. [Jaw. 



The habits of this fish are so peculiar as to deserve to be mentioned. 

 It derives its food from the green slime or moss that collects on the 

 surface of rocks under water, and which is removed with considerable 

 difficulty with the finger ; but so well has nature provided the creature 

 with the means of procuring its peculiar sustenance, that the object is 

 fulfilled with ease and apparent enjoyment. When feeding on the 

 upper surface of a stone, the animal glides forward with sufficient force, 

 and at the same time depresses the under lip, with which it scrapes 

 the slime off the rock as it passes over it, leaving a streak behind like 

 the scratch of a stick. If the food is to be derived from the side of a 

 rock, the creature accommodates itself accordingly ; and if from the 

 under surface of a projecting ledge, it throws itself on its back and 

 darts forward with the most wonderful agility. 



From observing these peculiai'ities of character it became necessary 

 to examine the anatomical structure of the mouth and digestive or- 

 gans of the animal, and the following is the result. 



The under jaw or rather the under lip (for it cannot be said to have 

 any jaws, and in this respect it resembles the sturgeon and loricaria), 

 is composed of three small bones, the two outer are articulated at their 

 bases to the inferior angles of the ossa malarum or cheek bones, (a 

 fig. 3. PI. I.)and the centre one is in like manner attached to the sternum 

 (b), these bones (1, 2, 3,) have hinge joints by which the lip may be 

 depressed at its free extremity, and they are attached laterally to each 

 other by strong ligaments. 



On the inner side of the bones of the lip is situated a strong mus- 

 cular mass (a fig. 4,) whose fibres originate on the inner side of the 

 sternum, and are inserted into the upper extremities of the bones and 

 ligaments of the lip, while that part of the organ which is used for 

 collecting food in the manner above described, is at once protected and 

 adapted to the performance of its singular function by a thick carti- 

 laginous covering. Whether we contemplate the peculiar figure of 

 the ossa malarum, the sternum, or of the muscles, nothing can be more 

 simple or complete than the means resorted to by Providence in adapting 

 the lip of this creature to the peculiar office it is destined to perform. 



From the unyielding nature of the abutments to which the lip is 

 attached in order to enable it to resist the pressure it is exposed to, 

 as well as from the peculiar nature of the joint, it is incapable of any 

 other action than that of being depressed ; but owing to its great 

 strength and necessary thickness, this motion alone would not be 

 enough to open the mouth sufficiently for the admission of food, and 

 this brings us to another contrivance still more curious. 



There is a small bone (c fig. 3.) loosely attached to what may be 

 named the nasal process of the frontal bone, by a hinge joint which 



