3-1 THE FKESII-WATEK FLSIIES OF ET'ROPE. 



mouth, its backward extension, and the breadth of the upper jaw behind, 

 there is but little space for the front portion of the sub-orbital ring-, which 

 is therefore small, and the cavities of the cephalic canal in this region are, 

 therefore, less obvious than in Acerina; the other portions, however, of this 

 vascular mucus system are more strongly developed, and the head appears to 

 be surrounded by mucus vesicles. The external apertures of the nares, which 

 are anterior and posterior to each other, are separated by a broad process of 

 membrane. 



The first portion of the dorsal fin commences over the base of the 

 pectoral fin. Its rays radiate, but the last is the shortest, and is joined by 

 membrane to the succeeding- longer ray which Nordmann included in the 

 second dorsal, but which is not very distinctly separated from the first 

 dorsal, so that it is almost a matter of taste whether the fish is accredited 

 with one or two dorsal fins. The second dorsal includes three spines, and nine 

 to eleven soft rays. The termination of the soft part of the fin is exactly 

 opposite to, and coincides with, the termination of the anal fin, though the 

 anal commences somewhat farther back, immediately behind the conspicuous 

 ovarian papilla. The anal aperture is nearly in the middle of the length 

 of the body. The ventral fins are close under the bases of the pectoral fins, 

 than which they are somewhat shorter, for the pectoral fins, when turned 

 back, reach nearly to the anal aperture, and exceed in length the deeply-forked, 

 evenly-lobed caudal fin. 



The scales are all ctenoid, and rather delicate. There are thirty-four to 

 thirty-six scales along the lateral line, which have tubular perforations. The 

 number of scales is greater in the row which is next above the lateral line. 

 There are no scales on the head and throat. 



The colour is yellowish-white, shading* into violet on the back, with the 

 sides, operculum, and belly like burnished silver. The base of the dorsal fin 

 is marked by numerous round brownish-black spots, which extend to the 

 caudal fin. The lateral line is margined by spots of black pigment. 



Nordmann, who first found this interesting- species at Ackermann, in 

 Bessarabia, states its size to be rather smaller than Acerina cernua. 



Heckel and Kner describe it from the Dniester ; Dr. Grimm states that 

 it is found in the Black Sea, at the mouths of the Dniester, Bug, and 

 Dnieper. 



