the transverse series, generally in that running from the commencement of the dorsal fin, or the middle of the back to the lateral line, and from the lateral line down to the vent or ventral fin, or middle of the abdomen.[1]
Fig. 21.—Arrangement of scales in the Roach (Leuciscus ratilus): L I = Lateral line; t r = Transverse line. a. Transverse line from lateral line to ventral fin.
The scales of many fishes are modified for special purposes, especially to form weapons of defence or a protective armour, but the details of such modifications are better mentioned under the several families in which they occur. All scales are continually growing and wasting away on the surface, and it seems that some fish, at least,—for instance, Salmonoids—"shed" them periodically; during the progress of this shedding the outlines of the scales are singularly irregular.
- ↑ In the formula generally preceding the description of a fish, "L. lat. 40," would express that the scales between the head and caudal fin are arranged in 40 transverse series; and probably, that the lateral line is composed of the same number of scales. "L. transv. " would express that there are eight longitudinal series of scales between the median line of the back and the lateral line, and five between the lateral line and the middle of the abdomen.
