482 Percomorphi 
from the lower Eocene near London. Several other tunny- 
like fishes occur in the lower Tertiary. 
The Escolars: Gempylide.—More predaceous than the mack- 
erels and tunnies are the pelagic mackerels, Gempylide, known 
as escolars (‘‘scholars’’), with the body almost band-shaped 
and the teeth very large and sharp. Some of these, from 
the ocean depths, are violet-black in color, those near the 
surface being silvery. Escolar violaceus lives in the abysses 
of the Gulf Stream. Ruvettus pretiosus, the black escolar, 
lives in more moderate depths and is often taken in Cuba, 
Madeira, Hawaii, and Japan. It is a very large fish, black, 
with very rough scales. The flesh is white, soft, and full of 
oil; sometimes rated very high, and at other times too rank 
to be edible. The name escolar means scholar in Spanish, but 
its root meaning, as applied to this fish, comes from a word 
meaning to scour, in allusion to the very rough scales. 
Promethichthys prometheus, the rabbit-fish, or conejo, so- 
called from its wariness, is caught in the same regions, being 
especially common about Madeira and Hawaii. Gempylus 
serpens, the snake-mackerel, is a still slenderer and more voracious 
fish of the open seas. Thyrsites atun is the Australian ‘‘barra- 
cuda,’’ a valued food-fish, voracious and predaceous. 
Scabbard- and Cutlass-fishes: Lepidopide and Trichiuride. — 
The family of Lepidopide, or scabbard-fishes, includes degen- 
erate mackerels, band-shaped, with continuous dorsal fin, 
and the long jaws armed with very small teeth. These are 
found in the open sea, Lepidopus candutus being the most 
common. This species reaches a length of five or six feet 
and comes to different coasts occasionally to deposit its spawn. 
It lives in warm water and is at once chilled by the least cold; 
hence the name of frostfish occasionally applied to it. Several 
species of Lepidopus are fossil in the later Tertiary. Lepido- 
pus glarisianus occurs in the Swiss Oligocene, and with it 
Thyrsitocephalus alpinus, which approaches more nearly to the 
Gempylide. 
Still more degenerate are the Trichiuride, or cutlass-fishes, 
in which the caudal fin is wanting, the tail ending in a hair-like 
filament. The species are bright silvery in color, very slender, 
and very voracious, reaching a length of three to five feet. 
