432 CHUSTACEA. 
This extraordinary genus has been considered as affording proof of the relation of the Trilobites to the Isopodous 
Crustacea, the body being divided into three longitudinal portions, as in those fossils. The genus has lately been 
described and figured in detail by Eights, under the name of Brongniartia Trilobit aides, in the Transactions of the 
Albany Institute.^ 
In the other Cymothoada the eyes are lateral, and not placed upon tubercles, and the tail is composed of four or 
six joints; of these the majority have the eyes not formed of granular ocelli; the antennae are at least seven- 
jointed, and the six fore-legs terminated by a strong hook ; of these the following subgenera have the tail always 
six-jointed, and the lower antennae never exceed in length half of the body. 
Cymothoa, Fab., having the mandibles not exposed, the antennae of nearly equal length, the eyes slightly appa- 
rent, and the terminal joint of the tail transverse-quadrate. Type, Cymothoa (Estrum, Fab. [These animals were 
well known to the ancients, who gave them the name of (Estrus and Asilus, from the resemblance between their 
habits and those of the breeze-flies. Aristotle says of the species above mentioned, “ Fishes are attacked by a 
sea-louse, w'hich is not produced from the fish but from the mud.”] 
Ichthyophilus, Latr. {Nerocila and Lironeca, Leach,) differs from the last in having the terminal segment of the 
tail nearly triangular. To these succeed various subgenera, instituted by Leach upon strucUiral characters, such 
as the relative length of the antennas, form of the swimming plates of the tail, &c. 
In (Ega, and several others, the eyes are generally large, and converge anteriorly. 
Synodus, Latr., having also six segments to the tail, differs from all the preceding in the large size of its 
exserted mandibles. 
Cirolana, Leach, and several others, have only five segments in the tail, and the length of the inferior antennae 
is greater than that of half the body. 
Eurydice, Leach, belonging to this division, naturally conducts us in the granular structure of its eyes to 
Limnoria, Leach, in which these organs resemble numerous ocelli, placed close together, which have the antennae 
inserted in a line, and not composed of more than four joints, and all the legs are formed for walking. The tail is 6- 
jointed, the terminal joint being large and suborbicular. The only known (recent) species is the L. terebrans, Leach, 
which, although not more than a sixth of an inch in length, is, in its powers of multiplication, exceedingly destruc- 
tive. It pierces the wood of vessels in different directions with astonishing alacrity, and contracts itself into a 
ball when alarmed. It is found in different parts of the British Ocean, [attacking piles of wood immersed in the 
water in our dockyards, flood-gates, timber-bridges, chain-piers, &c., and which it perforates in a most alarming 
manner. The boring of the insect having for its object the procuring of food, the contents of its stomach resem- 
ble comminuted wood. It is necessary that the hole in which it is at work should be filled with salt water. 
Coating the wood with copper-headed nails, and the use of Kyanized wood, have been suggested as remedies against 
its attacks]. 
Professor Germar forwarded to Dejean the figure and description of a small fossil crustaceous animal, which 
appears to us to belong to this subgenus. 
The third section, Sphjeromides, Latr., exhibits four distinct and setaceous or conical antennae, ter- 
minated (except in Anthurd) by a multiarticulate filament : the lower pair is always the longest, and 
inserted beneath the basal joint of the upper, which is thick and broad. The mouth is of the ordinary 
form. The branchiae are vesicular or soft, naked, and disposed longitudinally in pairs. The tail is only 
composed of tw'o complete and moveable segments, the first of which, however, exhibits impressed 
and transverse lines, indicating the vestiges of the same number of segments. On each side of the pos- 
terior extremity of the body is a swdmmeret , terminated by two plates, of which the inferior alone is 
moveable, and the upper is formed by an extei’nal elongation of the common support. The branchial 
appendages are curved inwards ; the inner side of the anterior pair is accompanied in the males with a 
small linear and elongated piece. The anterior part of the head, situated beneath the antennas, is 
triangular, or in the shape of a heart reversed. The majority have the body oval or oblong, assuming 
the form of a ball when contracted. 
Zuzara, Leach (with very large swimmerets), and Sph<eroma, Latr. (with moderate sized-swimmerets), have the 
impressed lines on the basal segments of the tail not extended to the sides. In the following they extend to the 
margin, forming as many incisions, and the basal joint of the antennse forms a long square or linear plate. 
Noesa and Campecopcea, Leach, have the sixth segment of the body considerably longer than the preceding, 
whilst it is of equal size in 
Cilic(ea, Leach, Cymodocea, Leach, and Dynamene, Leach, distinguished by variations in the form of the 
swimmeret and the sixth segment of the body. 
Anthura, Leach, differs from all the preceding in its vermiform body, and in having the antennae scarcely as 
long as the head, and 4-jointed. The plates of the swimmeret form a kind of capsule. (Oniscus gracilis, Mon- 
tague.) 
In the fourth section, Idoteides, Leach, the antennae are also four in number, but placed in the | 
same transverse and horizontal line ; the lateral ones are terminated by a multiarticulate and gradually | 
attenuated filament, the intermediate short, filiform, or slightly thickened at the tip, and 4-jointed, | 
none of the joints being articulated. The mouth is composed of the same parts as in the preceding. ' 
