68 THE FRESH-WATER FISHES OF EUROPE. 



silvery band ; but the pale olive-green scales on the back adhere better. 

 Black pigment is scattered over the scales of the back, forming a sort of net- 

 work. There are four rows of scales above the lateral line, and six or seven 

 below. The scales are broadly pentagonal, with rounded corners. The 

 middle scales are about one-fourth of the orbital diameter. There are forty- 

 three or forty-four vertebrae. The extremity of the swim-bladder is enclosed 

 by processes from the nineteenth and twentieth vertebrae. 



The fish is found in the Lake of Albano, in Italy, where it may be three 

 inches long ; in the Lake of Nemi it may exceed four inches. 



FAMILY: MUGILID^. 



GrENUS : MUgll (ARTKDl). 



The Grey Mullets are migratory fish, found in all temperate and tropical 

 regions. They enter fresh waters, but always pass a portion of the year in 

 the sea. They have an oblong compressed body, on which there is no lateral 

 line. The cleft of the mouth is transverse, and short. The jaws are without 

 teeth. The mandible sometimes has the anterior margin ciliated, and it is 

 always sharp. The eyes are placed laterally. The gill-openings are wide. 

 There are five or six branchiostegal rays. There are two dorsal fins; the 

 anterior dorsal is longer than the second dorsal, and contains four stiff spines. 

 The ventral fins are abdominal in position, and attached to the elongated 

 coracoid bone. 



Dr. Giiuther observes that fishes of this genus feed on organic substances 

 which are found mixed with sand or mud, and that the mud is worked for 

 some time between the pharyngeal bones, when the roughest materials are 

 ejected from the mouth. 



The pharyngeal bones have an arched irregular form, tapering in front. 

 They are covered with a membrane, which is studded with horny cilia, and 

 rest upon a mass of fat. Each branchial arch carries close-set gill-rakers, 

 which fit into those of the adjacent arch, forming a perfect filter. 



The stomach is remarkable for its muscular character. In structure it re- 

 sembles the stomach of a bird. There is a first membranous portion, which is 

 globular, and a second portion, which is formed by an exceedingly strong 

 muscle, of equal thickness in the whole circumference. The internal cavity 

 of the stomach is small. A small circular valve in the pyloric region divides 



