Page:Natural History, Fishes.djvu/255

Rh near the middle of the back. The body is more compressed than in the Salmons, and in most of the genera the belly is very thin, forming a sharp edge, frequently cut into saw-like notches, by the projecting scales, the points of which are directed backwards.

The mouth is small and oblique, either furnished with minute teeth, or altogether destitute of these organs; the lips are very thin. The opening of the gills is more than usually wide; hence, by a law already alluded to, the Herrings can survive a removal from the water for only a very brief period. The common Herring and Pilchard are said to die in a few minutes after being caught. The stomach is a lengthened sac; the intestines are furnished with many cæca; and there is generally a long and pointed air-bladder.

The skeleton of fishes generally consists of a greater number of bones than that of other animals. The ribs are long and slender spines, but there are many other bones besides the ribs, supernumerary, or rather accessory, spines, which spring from the bases of the ribs, and other parts of the vertebræ. In the Herring family these spinous appendages are peculiarly developed; for they are long, and attached not only to the rib-bases, but to each of the spinous processes of the vertebræ, so that each of these joints carries three pairs of accessory spines, besides a series of slender diverging bones that run along the line of the abdomen.