SAND EELS AND THEIR ALLIES 2809 



as a marine representative of that genus. The common ling, which 



generally measures from two to three feet in length, is a northern 

 Rockhngs fe 



form, ranging from the coasts of Greenland and Iceland to those of 



Britain and other parts of Northern Europe. In this fish the upper jaw is the 

 longer, but the reverse condition obtains in a second Scandinavian species, and also 

 in a third from the Mediterranean, which are the only other representatives of the 

 genus. The ling fishery is an important industry, large quantities of these fish 

 being cured and dried. Belonging to the same group of the family as the ling, the 

 rocklings (Motella) are readily distinguished by the reduction of the first of the 

 two dorsal fins to a narrow-rayed fringe, with the first ray elongated, more or less 

 completely received in a longitudinal groove. There is a band of teeth in the jaws, 

 and another on the vomer, and all the species have barbels, not only on the chin, 

 but likewise on the muzzle, the number of these appendages affording the readiest 

 means of specific discrimination. They are all of small size, and while ranging over 

 the same seas as the ling, likewise extend to those of Japan, the Cape, and New 

 Zealand. The British representatives of the genus include the five-bearded rock- 

 ling (J/.' mustela) with four upper barbels, the four- bearded rockling (M. cimbria), 

 and the common three-bearded rockling ( M. tricirrhata) ; the little fish commonly 

 known as the mackerel midge, and formerly regarded as the representative of a 

 distinct genus being only the young of the rocklings. 



Brief mention may be made here of a fish from the Northern, Temperate, and 

 Arctic seas, known as the torsk {Brosmius brosme), on account of its forming the 

 sole representative of a group characterized by having only a single long dorsal and 

 a shorter single anal fin, the caudal being distinct, the narrow pectorals formed of 

 five rays, teeth present on the vomer and palatines, as well as in the jaws, and the 

 chin furnished with a barbel. Attaining a length of a little over twenty inches the 

 torsk is occasionally taken in the Firth of Forth, and is abundant round the Shet- 

 lands and Orkneys. 



SAND EELS AND THEIR ALLIES Family OPHIDIIDSE 



In this rather small family, almost all the members of which are marine, the 

 pelvic fins, if developed at all, are rudimentary; there is no separate anterior dorsal 

 or anterior anal, and the caudal is generally confluent with the median fins. In 

 form the body is more or less elongate, but it may be either naked or scaled. The 

 dorsal fin occupies the greater portion of the back; the rudimentary pelvics are 

 jugular in position; the gill openings are wide; and the gill membranes are not 

 attached to the isthmus. While some of these fishes are deep-sea forms, others are 

 littoral. The family may be divided into five subfamily groups. 



The most remarkable representatives of the first subfamily (in 



which pelvic fins, attached to the pectoral girdle, are always present) 



are two small fishes from the subterranean fresh waters of certain caves in Cuba, 



constituting the genus Lutifiiga. They are totally blind, with the eyes rudimental 



and covered with skin, or wanting, and always live in perpetual darkness. The 



