ICHTHYOLOGY. 



figure of the body, and of otber remark- 

 able parts. The characters of the species 

 are taken chiefly from the number of 

 rays in the fins, which differs in the dif- 

 ferent species. But as the precise enu- 

 meration of these rays is sometimes a 

 matter of difficulty, and as they are like- 

 wise subject to variation, it is necessary 

 to have recourse to other marks, and to 

 adopt, as subsidiary characters, the form 

 and situation of particular fins, the pro- 

 portion of the head to the body, the con- 

 dition of the lateral line, the number of 

 the vertebrae and ribs, &c. 



Mr. Pennant describes fishes under the 

 three great divisions of cetaceous, cartila- 

 ginous, and bony. The latter, which is by 

 far the most numerous, he subdivides into 

 Four sections, entitled, agreeably to the 

 Linnaean orders, apodal, thoracic, jugu- 

 lar, and abdominal. 



The shape of the body of fishes is sub- 

 ject to considerable varieties. It is said 

 to be compressed, when the diameter, 

 from side to side, is less than from back 

 to belly ; and depressed, on the contrary, 

 when the diameter, from side to side, is 

 greater than from back to belly. It is 

 cylindrical, when it is circular in the 

 greater part of its length ; ensiform, or 

 sword-shaped, when the back and belly 

 terminate in a sharp edge, or when the 

 body gradually tapers from the head to 

 the tail ; cultrated, or knife-shaped, when 

 the back is somewhat flat, and the angle 

 below acute ; carinated, or keel-shaped, 

 when the back is rounded, and the under 

 part of the belly acute, through its 

 length; oblong, when the longitudinal 

 diameter is much longer than the trans- 

 verse; oval, when the longitudinal dia- 

 meter not only exceeds the transverse, 

 but the base is circular, and the apex 

 more acute ; orbicular, when the longitu- 

 dinal and transverse diameters are nearly 

 equal; cuneiform, or wedge-shaped, when 

 the body gradually flattens towards, the 

 tail : conical, when it is cylindrical, and 

 grows gradually more slender towards the 

 tail ; ventricose, when the belly is very 

 prominent; gibbous, when the back pre- 

 sents one or more protuberances ; annu- 

 lated, when the body is surrounded by 

 rings, or elevated lines; articulated, when 

 it is covered with connected and bony 

 plates ; trigon, tetragon, pentag.cn, and 

 hexagon, when the sides are plain, with 

 three, four, or six longitudinal angles ; if 

 the number of these angles exceed six, it 

 is termed a polygon. 



The surface of the body of fishes is 

 termed naked, when it is destitute of 



scales ; scaly, when provided with them; 

 smooth, when the scales are without an- 

 gles, furrows, roughness, or inequalities ; 

 lubricous, or slippery, when invested with 

 a mucous or slimy humour ; tuberculated, 

 or rough, when covered with prominent 

 warts or tubercles ; papillous, when co- 

 vered with fleshy points ; spinous, when 

 the asperities are elongated, and pointed 

 at their extremities ; loricated, or mailed, 

 when the body is enclosed in a hard, cal- 

 lous, or bony integument, or in scales so 

 closely united as to seem but one ; fasciat- 

 ed, or banded, when marked with trans- 

 verse zones from the back to the belly ; 

 striped, when marked with very narrow,- 

 scattered and coloured streaks ; vitiated, 

 when marked with longitudinal zone* 

 along the side, from the head to the tail ; 

 reticulated, or chequered, when marked 

 with lines forming the appearance of net- 

 work ; pointed or dotted, when marked 

 with points, either longitudinally dispos- 

 ed, or without order; and variegated, 

 when of different colours. 



The head is always placed at the ante- 

 rior part of the body, and reaches from 

 the extremity of the nose to the gills. The 

 head contains the mouth, nose, jaws, lips, 

 teeth, tongue, palate, nostrils, eyes, bran- 

 chial opercules, the branchiostegous 

 membrane, the aperture of the gills, and 

 the nape. The branchial opercules are 

 scaly or bony processes, situated on both 

 sides of the head, behind the eyes, clos- 

 ing the aperture of the gills, and sustain- 

 ing the branchial membrane. The bran- 

 chial, or branchiostegous membrane, is 

 true fin, formed of cartilaginous crooked 

 bones, joined by a thin membrane, lurk- 

 ing under the opercula, to which it ad- 

 heres, and is capable of being folded, or 

 expanded, as necessity requires. 



The trunk is that part of the body 

 which extends from the nape and branchi- 

 al aperture to the extremity of the tail. 

 It comprehends the gills, throat, thorax, 

 back, sides, abdomen, lateral line, anus, 

 tail, and scales. The gills, or branchix, 

 consist, for the most part, of four crook- 

 ed, parallel, unequal bones, furnished 

 on the outer, or convex part, with small 

 soft appendages, like the beards of a fea- 

 ther, and generally of a red colour. 



The fins consist of several rays, con- 

 nected by a tender film or membrane; 

 and they are raised, expanded, or moved, 

 in various directions, by means of appr" 

 priate muscles. The rays of the fins are 

 either jointed and flexible small bones> 

 whose extremity is often divided into 

 two parts, or hard and prickly, without 



