120 



Part III. — Twenty-fourth Annual Report 



case of the ventral and pectoral fins the most dorsal ray — in the case of 

 the first dorsal fin, the most anterior ray — to the tip of the longest ray. 



Height of the Lateral Line above the Lateral Axis. — The lateral 

 axis is here taken as coinciding with the straight posterior part of the 

 lateral line. This line was continued by a thread on the measuring board 

 along the fish, and the interval between it and the lateral line was 

 measured at two points — viz., at the level of the anus and at the level of 

 the base of the pectoral fin. In luscus, in place of the measurement at 

 the pectoral fin, which is very close to the anus, a new point at the 

 middle of the first dorsal fin was chosen. 



Length op the Rami of Tail-Fin. — That is, the distance from the 

 base of the first fin-rays of the caudal fin on the dorsal or ventral line of 

 the body to the tip of the ramus of the tail. 



The Spread of the Tail. — The greatest breadth of the tail-fin. For 

 the purpose of this measurement it is not spread out to its fullest extent, 

 but is allowed to fall on the table. 



Length of the Caudal Peduncle : dorsal. — The part of the dorsal 

 edge between the end of the third dorsal fin and the beginning of the 

 caudal fin. 



Greatest Height of the Unpaired Fins. — The fin is stretched out, 

 and its greatest breadth is measured, i.e., between the base and the highest 

 point vertically above the base. This is a character which it is often im- 

 possible to get, owing to the fact that in trawled fish the fins are usually 

 frayed or broken. 



The above measurements of the eye, interorbital space, of the fins, and 

 of the height of the lateral line were made by means of dividers. 



The Distance of Different Points from the Anterior Tip of the 

 Fish. — The anterior tip of the fish is in luscus and minutus the tip of the 

 upper jaw, in esmarkii the tip of the lower jaw. The distance of each 

 point was measured as projected on the lateral axis. The lateral axis is 

 the line joining the anterior tip to the middle rays of the tail-fin. 



These points are : — 



Anterior edge of the orbit (for the length of the snout). 

 The base of the first fin-ray of the ventral fin. 

 The base of the first fin-ray of the pectoral fin. 

 The opercular cleft. 



The hindmost part of the edge of the operculum. 

 The anus. 



Beginning and end of each of the unpaired fins. 

 Beginning of the caudal fin, dorsal and ventral. 

 Tip of the ramus of tail, dorsal and ventral. 



Point where the lateral line begins to rise up off the horizontal — the 

 anterior end of the straight part of the lateral line. 



The beginnings of the fins were marked by means of pins inserted at 

 the base of the first ray. A pin inserted in the anus was taken as the 

 position of the anus. A pin lying in the opercular cleft indicated that 

 point. 



For the purpose of these measurements a measuring board, similar to 

 that which was used during the research on the "Mackerel of the East 

 and West Coasts of Scotland" (Eighteenth Annual Report of the 

 Fishery Board for Scotland, Part III., p. 295), was employed. The 

 measurements made on the soft body of the fish are not such as permit of 

 exact determination, and probably the errors due to the want of rigidity is 

 greater in small fish than in large specimens. There is, however, 



