420 



CRUSTACEA. 



claws are nearly equal, cnitsi.stini,^ also of a siii:::,"le iyxjcics, (A. lii/s .slirhiiiic'iiin, Leach) fonnd upon tht? coasts of 

 Eni^^laiiil and rraiicc. 



AiiiniiL,^st tbiiM.'spM'ies \'iliich linve Ihe six forc-IcL^.s funning' as many didactylc claws— (.n cliaractrr wliicli removes 

 them from all th*- piecediii;: liecapods, and in which they are related to the species at the head of the followinff 

 section— from which, however, they diiler in the fore-claws beino; hy far the largest, the peduncle of the lateral 

 antenna furnished with a scale or spines, the outer plate of the swinimeret at the extremity of the tail appealing- 

 in all the recent species, as though it is divided into two parts by a transverse suture,)— are the following g^enera. 

 En/on, Desm., comprises a single singular fossil species found in the calcareous stone used for lithography at 

 Pappenheim and Aichtedt, in Anspach. The carapax is [very broad], and uith very deep lateral incisions. The 

 plates of the swimnjeret are pointed at the tip. 



The genus Astacus, Gronovius, Fabr., have the lateral plates of the swimmeret hroad and rounded at the ex- 

 tremity; the two exterior ones with a transverse suture. The tuo tilaments of the intermediate antennae are 

 longer than their peduncles, with the sides of the carapax entire. 



In the marine species of this genus, the middle plate of the tail does not exhibit a transver^^e suture. Of some 

 of these, Leach has formed his genus Nephi-ops^ characterized by the large scale of the lateral antenna:', and the 

 long prismatic claws of the fore-legs. Type, Cancer norvegicus, Linn., a species found on our coast. The 

 others having the lateral antennre only furnished with two short teeth or spines, and the fore-claws large and ovat, 

 form the restricted genus Avhuu.^-, Lca-h, tlu^ type uf which Is th^ connmrn Lcb-tcr {('ann-r .jnumfn n.s, Linn.; 

 .-l,v/(/r-//.v marimis, Fabr.), of which tlic mstrum in front y.\( thr ( ar.ipax is arnicd \ulli thru,' lucth un l;lc1i side, and 

 a dnu'ile tiioth at the base ; and the claws are very large, and unequal in size. The flesh is highly relished. It is 

 found ill the European Ocean, the Mediterranean, and on the coasts of North America. The internal structure 

 has Iteen studied with great diligence by MM. V. Audouin and M. Edwards. 



in the fresh-water species of this genus, the terminal segment of the tail, forming the middle idate of the s^\im- 

 meret, is transversely divided by a suture*; and the claws are rough, and finely toothed on the inside of the 

 fingers. The rostrum has a tooth on each side, and two at the base. It is ordinarily of a greenish-brown colour, 

 [but, like the lobster, changes to bright red by boiling]. From its common occurrence it has been greatly studied, 



not only as regards its anatomy, but also its habits, 

 and the peculiar power it possesses of renewing its 

 antennae and legs when thrown off or niutilattd. 

 The stomach contains, at the time of moulting, two 

 stony secretions, formerly used in medicine as ab- 

 sorbents,, but wliich are now replaced by carbonate 

 of magnesia. It hides itself under stones and in 

 burrows [in the banks of rivalet^ and streams], 

 ■whence it only conies forth in order to search fur 

 its hii.id, A\liii-h consists of small mollusca, small 

 fislics, and tiiL' l;irv;c of aquatic insects. It al-u 

 r,;. 11. —The CrnyOsh. fccds upou decaying flesh, and the carcases of ani- 



mals floating in the water ; and which is also useil 

 as a bait, being placed in the middle of a bundle of faggots, or in a net. Its moulting take-; place at the end of 

 the spring. Two months after coupling, the female lays her eggs, which are at tirst collected in a mass, and 

 attached, by means ofaviscid liquor, to the subabdominal false legs. They are ofabrightred colour, and in- 

 crease in size before they are hatched. The Craylish are at their birth wvy sntt, and completely resemble tinir 

 parent. They take refuge beneath her tail, where they remain several days nnril the difl-'erent parts of their bodies 

 have acquired a suflicient strength. Thry li\r to the aue nf twenty years, increasing in size in proportion to their 

 ag''. Those are preferred whicli are fnimd in rnnniiii; wjitcr. A singular Annelidous parasite {Branchiubdclia, 

 Odier, in Man. Soc. (VUi.-ii. AV(/., I'aris, \>. G9), first ubscrvcil by Rosrl, infests the branchia- of (he Crayfi.-h. 



Another species inhabits the fresh water of North Ainerica; and a third, according to Le Coiite, din.--, much in- 

 jury to the rice plantations of the same country .f 



The foiirtli section, Caride.s (Latr.), have tlic intermediate antenna" inserted higher than the lateral, 

 and the pi.'duncU; of the latter is covered by a large scale. The body is arclwd, as though huncli- 

 liackcd, and ol" a more slender consistence than in the preceding Crustacea. The front of the carapax 



' [Millie Edwards, fro 

 nnmuiiclfiture, luia Uil 

 ustiLueii, tlie uld ^i^ni 



r tl' 



■i.lriiily ii 

 > lust kn. 



■iipcr ninitc 



Thu.s he • 



ais the ( 



tivi 



1 Gjuicer, Phili/rarr. 

 rcnmrked, llint by e 

 blifjerl Co restrict t 

 ,in|inrtiiiit group, ii 

 tinctly known Xn any nati 



111. s wliiuh lliey ufl- clutirly entitled to 

 .inion Crab, which iH the true type of 

 ts; agfiiriNt which impropriety Mr. Bell 

 other term than Cftiieer to this ijeiiua, 

 word CiLiicer to ft finmll niiil coniparfi- 

 i sin]rle H]iCL-ies of whieh wfis probnhly 

 list ot early tiin<.-s. In like mnnner, lie 



has taken nway the name Ast-icus frurii llie LobHtur, aiitl jjiven it to 

 the Criiyliah, and proposcii the new name Homarus for the former: 

 thus doing injustice to Dr. Leach, who, in the manuscripts 

 quoted in the Entomologisl's CoiiipruiHinn (with which Milne 

 Edwards irJ cvidLTilly miacqiiaiMlcd), liad eallcfl the Lob.iter .-i.s^riv-s 

 ga-n.iiniin, uii'l Oil- Craylisli ri.(,iii.<jl,ui': JIuviiililis. it is pro]K'r, 



til a 



r hiul be* 



^-] 



t [The dcvclopemcnt of the embryo Cr. 

 i live sCi limed liy Ur. Tlathke, in a most elab 

 ncr, in his Uritcrtiichinigen ulier die Bild 

 Fliisshrehsen, fol. Lcip7. 1.S-J9. Some i.it. 

 searches of this author upon the subject u 

 fact that five larije folio plates arc ci>iiiplc;l 



velopement, and of tlie iio« h liati Uid in 

 possible to llr^i^'e at any utlnr iiukIh -^ino 

 not undergo any chaiij;e of furmwlmli i- 

 the name of nieiamorpho.sisi. A lull jili-n- 

 Is iivicrted in No. IS of the Zunl„,:i,;,l J 

 dcs Si.'icncrs Nuiurel/cs for August, 1>;:;I.] 



!/>;; mill Ki. 

 1 of tlic c'.. 



