NOM^EIDS AND MACKERELS 2739 



temperate seas. To enable them to keep up their constant rapid movements, their 

 muscles, which are consequently red in color, receive a much more abundant sup- 

 ply of blood than is the case with other members of the class, and their temperature 

 is thereby raised several degrees higher. Although spawning in the open sea, at 

 certain times of the year they make periodical migrations toward the shore in pur- 

 suit of the shoals of herrings and their fry on which they so largely subsist. In 

 time, the family dates from the lower Eocene deposits of Switzerland, where it is 

 represented by several extinct genera, and likewise by a species of sucking fish; 

 while many of the other existing genera occur in the latter deposits. 



The true mackerels are characterized by the first dorsal fin being continuous, 

 with feeble spines; the presence of five or six finlets behind the dorsal and anal; the 

 very small scales, which are evenly distributed over the body; the small size of the 

 teeth; and the two short ridges on each side of the caudal fin. Although there are 

 but very few species of mackerel, these have a very wide range; and the genus is 

 represented throughout the temperate and tropical seas, with the exception of the 

 Atlantic seaboard of temperate South America. The general coloration and form 

 of mackerels are too well known to call for description, and it will suffice to men- 

 tion that of the three European forms the common mackerel (5*. vemalis)* has no 

 air bladder, while the southern mackerel (S. pneumatophorus) takes its name from 

 the presence of that organ, which likewise exists in the Spanish mackerel (S. colzas). 

 In a fossil condition this genus occurs in the European Eocene and Miocene deposits. 

 Of the common mackerel, which is represented in the upper figure of the illustra- 

 tion on p. 2732, Yarrell writes that "the ordinary length varies from fourteen to 

 sixteen inches, and their weight is about two pounds each; but they are said to 

 attain the length of twenty inches, with a proportionate increase in weight. The 

 largest fish are not, however, considered the best for table. As an article of food, 

 they are in great request; and those taken in the months of May and June are gen- 

 erally considered to be superior in flavor to those taken either earlier in the spring 

 or in autumn. To be eaten in perfection, this fish should be very fresh." The 

 enormous takes of mackerel which occasionally reward the labors of British fisher- 

 men are too well known to need mention. 



_ . Under this general title may be included not only the fish to which 



the name tunny ( Thynnus mediterraneus} properly pertains, but like- 

 wise those commonly designated bonitos and albicores. The genus, which com- 

 prises some of the largest of all pelagic fishes, differs from the true mackerels by 

 the greater number (six to nine) of finlets, by the scales forming a kind of corselet 

 on the anterior part of the body only, and the presence of only a single longitudinal 

 ridge on each side of the tail. The tunnies have a geographical distribution coex- 

 tensive with that of the family; and in a fossil state are found in the Eocene 

 and Miocene deposits of the Continent. The common species, which attains a 

 length of over ten feet, and a weight of half a ton, is an occasional visitor to the 

 British coasts, and is abundant in the Mediterranean, where it has been regularly 

 fished for since very early times. At the present day specimens of a hundredweight 



*The author can neither admit the combination Scomber scomber as the title of this fish, nor that of Thynnus 

 thynnus for the tunny. 



