226 ZOOLOGY. 
are also very variable, in some seasons the returns hardly paying the expense 
of the expeditions. Some idea of the extent of the trade may be formed 
from the fact that, in a single year, upwards of 234,000 barrels were taken 
by Massachusetts fishermen alone. A closely allied, but smaller species, 
S. grex, or chub-mackerel, is distinguished by a dark spot at the tip of the 
lower jaw. S. colias, or the Spanish mackerel, is also much esteemed, but 
rarer than the two preceding. It is distinguished from S. vernalis by the 
fact that the transverse undulations do not cross the lateral line, as in the 
latter species. In S. vernalis, also, there is a dusky line beneath the lateral 
line, and a black spot at the base of the pectoral and ventral fins. Scomber 
vulgaris, or the common European mackerel, is represented in pl. 83, 
jig. 9. The genus Thynnvs, or tunny, is distinguished from Scomber by 
the presence of a corselet round the thorax, formed by scales larger 
and coarser than those of the rest of the body. There is a bony and 
elevated crest on each side of the tail. The anterior dorsal reaches nearly 
to the posterior. Numerous finlets behind the dorsal and anal fins. A 
single row of small pointed teeth in each jaw. The common tunny, 
Thynnus vulgaris, is a mackerel of a gigantic size, and famed for the 
excellence of its flesh, which tastes something like lean pork. Fish of this 
species are caught in immense numbers in the Mediterranean, and eaten 
both fresh and salted. The usual method of preserving them for any 
length of time is to cut them into slices, which are packed away in barrels, 
with layers of salt interposed. They are generally caught in nets. This 
species is of rare occurrence out of the Mediterranean, where it is met 
with in great shoals. But few are recorded as being caught off the United 
States coast; one specimen, taken near Cape Anne, weighed 1000 lbs., 
and was fifteen feet in length. In New England it is known as horse 
mackerel and albicore. A European specimen is figured in pl. 83, fig. 8, 
A second species, of much smaller size, is found in the Gulf of Mexico. The 
bonito is also a species of Thynnus (T. pelamys), differing mainly in several 
large longitudinal stripes below the lateral line. It is this species, among 
others, which causes the flying-fish to leave the water in order to escape from 
its terrible enemy. The flesh is greatly inferior to that of the common tunny. 
The genus Pelamys differs from the last, in having strong separated and 
pointed teeth. The principal species, P. sarda, also called bonito, is of rare 
occurrence in American waters, where it is known as the skip-jack, 
especially in Massachusetts. Cybium is without a corselet, and has large 
compressed sharp teeth; the palatines with short and even teeth. One 
species, C. maculatum, or spotted mackerel, is of rare occurrence on the 
American coast. The genus Xiphias, or sword-fish, has a spindle-shaped 
body, covered with minute scales, a single elongated dorsal fin, ventrals 
wanting, upper jaw elongated, forming a sword-shaped protuberance ; 
mouth without teeth. This curious genus, represented by Xiphias gladius, 
or the well known sword-fish (pl. 81, fig. 18), is generally distributed 
throughout the Atlantic, being found on both the European and American 
shores. It attains to a great size, being sometimes fifteen feet in length, 
and weighing many hundreds of pounds. The flesh, especially of the 
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