i 
BRANCIIIOPODA. 
443 
gradually pointed, and immediately behind them is a terminal, nearly semiglobular joint, replacing a tail, and 
I which IS furnished with an elongated tilament, probably an oviduct. I have obsei*ved near the middle of the 
fifth and four following pairs of feet a g^lobose body, probably analogous to the vesicles which these organs present 
in Apus. The only species, albida, Latr., is very small, and of a whitish colour. It is found in the River of Nice. 
2. The Aspidiphora, Latr., [or second principal group of the Phyllopodous BrancMopoda] have sixty 
pairs of legs, all of which are furnished on the outside, near the base, with a large oval vesicle, and of 
which the two anterior, much larger than the rest, and ramose, resemble antennae. A large shell covers 
the major part of the upper side of the body, almost entirely disengaged, (shield-like,) posteriorly emar- 
ginate, and liearing anteriorly, in a confined space, three simple sessile eyes, of which the two anterior 
are larger and lunular ; and two bivalve capsules containing the eggs, annexed to the eleventh pair of 
feet. Such are the characters of the genus 
Apus, Scop., (forming part of the genus Binociilus, Geoffrey, and Limulus, Mull.).— The body, including the 
shell, is oval, broader, and rounded in front, and narrowed behind, forming a tail ; but if we remove the shell, it is 
nearly cylindrical, convex above, concave and divided by a longitudinal canal beneath, terninating in an elongated 
cone. It is composed of thirty joints, equally diminishing in size towards the posterior extremity, and which, 
with the exception of the seven or eight terminal ones, bear the feet. The ten anterior segments are membranous, 
soft, and without spines, presenting on each side a small eminence, or knob, with only a single pair of legs to 
each. The others are more solid and horny, with a row of small spines on the outer edge : the last is longer than 
the preceding, nearly square, depressed, angular, and terminated by two filaments, or articulated setae. In some 
species, composing the genus Lepiclurus, Leach, there is a corneous elliptic plate. If the number of legs be one 
hundred and twenty, the terminal segments after the eleventh and tw^elfth must severally bear more than a pair of 
legs, (in which respect these animals approach the Myriapoda). The shell, perfectly disengaged beyond its an- 
terior attachment, covers the greater part of the body, and thus defends the anterior segments, which are of a 
j softer consistence than the others ; it consists of a large, corneous scale, very slender, nearly diaphanous, exhibit- 
I ing the superior teguments of the head and thorax united, and forming a large, oval shield, deeply incised at its 
posterior extremity. Its upper surface is divided by a transverse line, forming two united arcs, into two areas, 
the anterior of a semilunar form, corresponding with the head, and the other with the thorax. Tluj anterior is fur- 
nished with the three eyes, and the posterior is carinated dovm the middle. The shell is only fixed to the body at its 
anterior extremity, so that the back of the animal may be distinctly seen throughout its whole length. Immedi- 
^ ately beneath the frontal disc are placed the antennae and mouth. The antennae are two in number, inserted on 
I each side of the mandibles, very short, filiform, and composed of two equal joints. The mouth consists of a square 
' labrum ; two strong, corneous mandibles, destitute of palpi, and toothed at the tip ; a tongue, deeply notched ; two 
pairs of foliaceous maxillae, the superior spined, and ciliated on the inner edge, and the inferior resembling small 
false legs. They are terminated by a slender, elongated joint, prolonged externally at their base into an ear- 
shaped appendage, and bearing a kind of palpus. The legs, about one hundred and twenty in number, gradually 
diminish in size after the second pair ; they are all compressed, foliaceous, and composed of three joints, not 
including the two long filaments at the tip of the two anterior, and tlie two leafiets terminating the following, 
which may be regarded as the analogues of a claw, having the two fingers elongated, and converted into antenna3- 
like filaments ; upon the posterior edge of this joint is inserted a large branchial membrane, and the following, or 
the second, also bears on the same side an oval, vesicular, red sac. The opposite edge of these legs also exhibits 
four triangular, ciliated leaflets. The eleventh pair of legs is very remarkable ; the first joint exhibits, behind 
the vesicle, two circular valves, applied upon each other, formed of two plates, and inclosing the eggs, which re- 
semble small, red grains. All the individuals hitherto examined have exhibited this structure, and it has, there- 
fore, been supposed that each has the power of fecundating its own eggs, and that there are no males. 
These Crustacea inhabit ditches, lakes, and standing waters, generally in innumerable quantities. Raised thence 
by violent hurricanes into the air, they have been observed to fall like rain. They are generally found in spring 
and the beginning of summer. Their food principally consists of young Tadpoles. They swim well on the back, 
and when they burrow into the sand, they elevate their tails in the water. When first hatched they have only one 
eye, four legs, like oars or arms, with whorls of hairs ; the second pair being the largest. The body has no tail, 
and the shell only covers the front half of the body. The other organs are gradually developed during the succeeding 
moultings. 
The species being few in number, it is not necessary to form (as Leach has done) with those 
which have a plate between the tails, a distinct genus {Lepidurus, Leach), type, Monoculusapus, 
Linn. The ridge of the shield terminates in a small spine posteriorly, which is not the case in 
Apus cancriformis {Limulus palustris. Mull.), which latter is also destitute of a plate between the 
tail. This forms the type of the restricted genus Apus of Leach, who has also figured another 
species, A. Montagui. 
[Prosopistoma, Latreille, in Nouv. Mem. du Museum, is composed of a minute species from Mada- 
I gascar, exactly resembling a species of Gyrinus in its external appearance. It is figured in Gudrin, 
Iconographie Crust., pi. 34, 14. Eurypterus, Dekay, is composed of a very remarkable fossil animal, 
allied to Apus and other analogous genera, the head not being distinct from the body, which is 
oval, but attenuated behind, with two large dorsal eyes, and four pairs of legs, the fourth being- 
very large, and like broad oars. Annals Nat. Hist., New York, 1825, p. 375, t. 29.] 
