:}S;> THE FRESH-WATER FISHES OF EUROPE. 



The five rows of shields, which defend the body, are arranged in the 

 following way : first, a median row in the middle of the back ; secondly, a 

 lateral row above the middle of each side ; and thirdly, a row on each ventral 

 angle, which extends back to the ventral fin. As each of these scutes has a 

 sharp edge or keel running along its middle, they impart to the fish a 

 somewhat pentagonal aspect. Between these rows of plates the skin is not 

 entirely naked, but is partly covered with smaller shields or bony protuberances 

 of different forms and sizes, and is smooth where these are not present. But 

 towards the end of the tail the bony scutes are flat, small, quadrate in form, 

 and closely packed. They extend upon the upper lobe of the caudal fin. 

 There are two large scutes on the under side of the head, angular posteriorly, 

 which are placed behind the gill-aperture. All the smaller scutes are 

 extremely variable, differing in form and size with the age of the fish ; and 

 occasionally some of the larger scutes are lost. The fins are seven in number, 

 and are formed of closely-placed, compressed, and jointed rays, which are 

 usually curved, and finely denticulated on both sides. The first ray of the 

 pectoral fin is strong and bony ; the denticulations on the rays are directed 

 backwards, and are very unequally developed in different species, and are often 

 mere asperities. The dorsal fin is placed far back ; the anal is opposite to its 

 posterior part. The ventral fins are close in front of the vent and much 

 smaller than the pectoral fins, which are rather powerful and long. 



The vertebral column extends to the extremity of the upper lobe of the 

 caudal fin, within which it is directed upward with a strong curve. The upper 

 lobe of the fin is much longer than the lower, and makes some approach to the 

 scythe-like form sometimes seen in the tails of Sharks. The intestine is short ; 

 the fleshy stomach is divided by a pyloric valve from the small intestine. The 

 large intestine terminates in a spiral valve, like that which characterises the 

 intestines of Sharks and other fishes of Grunther's group, Palaeichthyes. The 

 liver is large and firm ; it forms two principal lobes and many accessory lobes, 

 and it surrounds the biliary duct. The pancreas is subdivided into numerous 

 pyloric appendages, and opens into the intestine by a wide outlet near to the 

 biliary duct. The kidneys are narrow in front, and wider posteriorly, and 

 extend behind the vent, where the urinary duct opens in a depression, which 

 also includes the apertures of the reproductive organs. 



The ovaries and milt both extend through nearly the whole length of the 

 ventral cavity. The ovaries are not in connection with an oviduct, and open 

 freely into the ventral cavity by a funnel-shaped process. The milt is an 

 agglomeration of small rounded bodies like currants. The air-bladder, which 

 lies behind the stomach, is a large long or oval sac, and opens by a pneumatic 

 canal into the dorsal wall of the oesophagus. 



