Order 1. Div. 11. BRANCHIOPODA. 443 



pra'lnally pointed, and immediately behind them is a terminal, nearly semiglobular joint, replacing a tail, and 

 which IS furnished with an elongated filament, probably an oviduct. I have observed near the middle of the 

 fifth and four following pairs of feet a globose body, probably analogous to the vesicles which these organs present 

 in Apus. The only species, E. alhida, 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^rancAeqporfa] have sixty 

 pairs of legs, all of which are furnished on the outside, near the base, with a large oval vesicle, and of 

 whidi the two anterior, much larger than the rest, and ramose, resemble anteniMe. A large §hell covers 

 the major part of the upper side of the body, almost entirely disengaged, (shield-like,) posteriorly emar- 

 ginate, aud bearing 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 



Apns, Scop., (forming' part Of the genus Binoculus, Geoffroy, and Limulus, Miill.). — The body, inchiding 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 tort'afds the posterior extremity, and which, 

 ■With the exception of the seven or eight temiinal ones, bear the feet. The ten apterior segments aye 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 liorny, with a row of sniall spines on the outer edge : the last is longer than 

 {he preceding, nearly square," depressed, angular, and terminated by two filaments, or articulated setae. In some 

 apecies, composing the genus Lepidiims, Leach, there is a corneous, elliptic plate. If the number of legs be one 

 hundred and twenty, the terminal segments after the eleventh and twelfth must severally bear more than a pair of 

 legs, (in which respect these animals approadi the Myriapoda). The shell, perfectly diseng^aged beyond its an- 

 terior attachment, covers the greater part of the body, and tints defends the anterior segments, which are of a 

 softer consistence than the others ; it consists of a large, corneous scale, very slender, nearly diaphanous, exhibit- 

 ing the superior teguments of the head and thorax united, and forming a large, oval shield, deeply incised at- its 

 f)Osterlor extremity. Its -upper surface is divided by a transverse line, forming two united arcs, into two areas, 

 the anteriorof a semilunar forni, corresponding with the head, and the other with the thorax. The anterior is fur- 

 nished with the three eyes, and the posterior is carinated down the middle. The shell is only fixed to tlie body at its 

 anterior extremity, so that tlie 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 

 each side of the mandibles, very short, filiform, and composed of two equal joints. The mouth Consists of a square 

 labnim ; two strong, corneous mandibles, destitute of palpi, and toothed at the tip ; a tongue, deeply notched ; two 

 pairs of foliaceous maxillae, the stipertor 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 the two leaflets terminating the following, 

 which may be regarded as the analogues of a claw, having the two fingers elongated, and converted into antennae- 

 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) vvith those 

 which have a plate between the tails, a distinct genus (Lepidurus, Leach), t>'pe, Monoculus apus, 

 Linn. The ridge of the shield terminates in a small spine posteriorly, which is not the case in 

 Apus cancriformis {Limulus pahtsfris, Miill.), which latter is also destitute of a plate between the 

 tail. This forms the type of the restricted genus Apu^ 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- 

 gascar, exactly resembling a species of GjTinus in its external appearance. It is figured in Guerin, 

 Jconographie Crust., pi. 34, 14. Euri/pterus, Dekay, is composed of a very remarkable fossil animal, 

 allied to Apiis 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.] Siomaifui. 



