260 THE FRESH- WATER FISHES OF EUROPE. 



height of the head ; its rays are similar to those of the dorsal fin, but lower, 

 and, like that h'n, partially enclosed between lateral borders of projecting 

 scales ; the last rays are a little elongated. The ventral fin is somewhat in 

 front of the middle of the body; its rays are not so short as those of the 

 anal, but are shorter than in any other fin. In the angle over the base of 

 the anal is a scale prolonged like a spine ; it has a soft point, and ex- 

 tends for half or two-thirds of the length of the fin. The pectorals are 

 pointed, measure more than half the length of the head, and are near to the 

 ventral edge ; the scales overlap them at the base. The terminal rays of the 

 deeply-forked caudal fin are shorter than the head ; the lower lobe is slightly 

 the longer. The middle rays of this fin have very numerous and finely-jointed 

 branches. 



There are eighty scales in the lateral line, and there are twenty or twenty- 

 two scales in vertical series over the ventral fins. The scales vary much in size. 

 At the sides they are largest, square, and nearly equal to the diameter of the 

 eye. On the dorsal part of the tail the scales are elongated, their free edges 

 are marked by pai'allel delicate rays which do not reach the middle of the scale. 

 The scales on the caudal fin have a peculiar character. The middle rays are 

 covered with larger scales, while on the upper and lower lobes the scales 

 become smaller. The upper surface of the large scales is again covered by 

 three or four smaller scales ; each of the long scales recalls the form and struc- 

 ture of the wing of an insect ; or, as it has a stalk firmly fixed in the 

 skin, it might be compared to a dicotelydonous leaf. As the mid-rib runs 

 through the leaf, so the stalk extends through the scale and sends out on each 

 side numerous accessory branches which spread over the surface of the scale 

 (Fig. 144) . In the middle of the tail are two shorter scales, perforated by fine 

 canals. The stalk of each scale and its branches are regarded as offshoots of 

 the mucus-canal of the lateral line, which in the region of the shoulder sinks 

 deeply under the scales and appears to be wanting in the body, but reappears 

 at the base of the caudal fin, branching in its upper and lower lobes with the 

 finest ramifications. The cephalic canals are well developed and extend on to 

 both sides of the fore part of the trunk. The shoulder region behind the 

 angle of the gill-opening is ornamented with a black spot on which skin extends, 

 which, like that of the cheeks and operculum, shows innumerable dendritic 

 branches, none of which penetrate the substance of the scales. 



Another peculiarity of this fish is seen in the structure of the saw-like 

 ventral edge, for though the serrations are formed by the projecting scales, 

 the sternal ribs extend down to them, and Dr. Giinther describes this arrange- 

 ment as recalling the structure of the sternal ribs in the crocodile. 



The Shad feeds on small fishes and on vegetable substances. The in- 



