of the Fishery Board for Scotland. 



295 



I. Girth of Body at three points — (1) pectoral region, close to the hind border of 



the operculum {G. Pect.*), (2) at the beginning of the second dorsal fin 

 (G. '2nd 1).), (.'>) at the narrowest part of the root of the tail (G. T. )• The 

 measurements were made by means of a thread. 



II. The length of the Dorsal Groove (/ D. groove), which encloses the base of 



the first dorsal fin. 



III. The length of the Pectoral Fin {I Pf.), measured from the proximal 



end of the first or superior ray to the tip of the fin. 



The following are measurements made on the lateral axis (" principal 

 axis " of Heincke). The lateral axis is a line drawn from the tip of the 

 mandible, when the mouth is closed, to the middle of the fork of the tail. 

 From certain points on the body of the mackerel (vide diagram), per- 

 pendiculars were drawn to the lateral axis, Oa. The distances from zero 

 (the tip of the snout) to the points where the perpendiculars cut the axis 

 were measured. These dimensions are as follows: — 



* These symbols refer to the headings in the Tables appended, 



