~20 ZOOLOGY. 
and sharper teeth. In it is the species HZ. vulgaris, or halibut, found on 
the coasts of both Europe and America. It attains to a very large: size, 
individuals of even 500 and 600lbs. having been met with. Its flesh is 
highly prized, and the fins are world-renowned as an epicurean morsel. In 
Rhombus both the eyes and color are on the left side: the dorsal com- 
mences anterior to the eye: dorsal and anal fins extend nearly to the tail. 
Teeth exist both in the jaw and pharynx. Conspicuous in this genus is 
Rhombus maximus, or the turbot, celebrated as the best of all European 
fishes. A turbot, probably of a different species, has recently been 
detected off the coast of Massachusetts. Pl. 81, fig. 8, represents 
Rhombus vulgaris, or the brill, a common European species. The genus 
Achirus is without pectoral fins, and_has the eyes on the right side of the 
head. Mouth distorted to the side opposite the eyes, and very small. Dorsal 
and anal not united to the tail, as is the case in the genus Plagusia. The 
Achirus mollis, or common sole, is very abundant on the Atlantic coast of the 
United States. P/. 82, fig. 11, represents the Solea vulgaris, European sole. 
The family Ecuinerpa is represented by the genus Hchineis, which 
comprehends fishes with a flattened disk upon the top of the head; this 
being composed of a variable number of cartilaginous plates, movable in 
such a manner as to admit of their being attached by suction to an object 
in the water. A single dorsal opposite the anal. Teeth on the jaws, 
vomer, and tongue. Pl. 84, fig. 3, represents the Echineis remora, or 
sucking-fish, found throughout the Atlantic ocean. There are additional 
species with various characters. 
We come now to an order of fishes, Acanthopteri, corresponding nearly 
with, but rather more restricted than, Acanthopterygit of Cuvier. This 
order is characterized by the ctenoid scales, the advanced ventrals, the - 
spinous fins, &c. It embraces many species of considerable value. The 
first family, Percrpa, is known by the rough scales, the dentated oper- 
culum or preoperculum, and the occurrence of teeth in the jaws, the front 
of the vomer, and generally on the palatines. 
The number of genera and species in this family is very great, distributed 
as they are over the entire globe, and occupying both salt and fresh water. 
Two principal types may be distinguished, one with a single continuous » 
dorsal, the other with this dorsal more or less deeply divided, and separated 
into two. The typical genus is that of Perca, with two separated dorsals, 
the rays of the first spinous, of the second flexible ; teeth in both jaws, in 
front of the vomer, and on the palatines; tongue smooth; operculum with 
a short, flattened, backward spine. Perca fluviatilis, the most common 
European species, is figured in pl. 82, fig. 4. Numerous species occur in 
North America, the most conspicuous of which is the Perca flavescens, or 
common yellow perch, which is found in almost all sorts of situations, both 
salt-water and fresh. Several closely allied species occur in the different 
lakes and rivers of the North American continent. The genus, or rather sub- 
family, Etheostoma, is altogether peculiar to North America, where nearly 
every large river has one or more species peculiar to it. They are all of 
rather small size, some of them very minute. Professor Agassiz has recently 
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