448 CRUSTACEA. 



DicJielestium, of the younger Hermaim, has the body narrow, elong-ated, slightly dilated in front, and comi''isr'd 

 of seven segments, the anterior beinp; larger, rhomboidal, and composed of the head and jmit "f tlie thorax unitpd. 

 It supports, 1, four short antenna', the lateral ones being lilifurm, 7-jfiintPd, nuil the inti'iini.tliido pair advanc-'d 

 like short arms, 4-joii]t(jd. A\ith the last in the form of a diihirl \ N; claw ; -j, ;l siidnin on its umhT-Mdr, rni.-n- 

 branoLis and tubular; 3, three Kinds of mis-shapen palpi (two liiany-rlcti icgsVj nu carh side, situHtcu on an ele- 

 vation; and, 4, four feet fitted for prehension, of which the t\\o anterior are tenninated by several anequal- 

 sized, tniithcd lic^ks, and of «hich the second pair are terminated by a strong hook. Each of tlie second and third 

 segnnents supports a pair of legs fonned of a joint terminated by two kinds of lingers, tootlied at the Tip, To the 

 fourth segment is attached a fifth pair of legs (the last), being in the form of simplf, oval, and immovable vesicles, 

 which Hermann regarded as ovaries rather than legs. The hind se[niient is flattened, and terminated by two minute 

 vesicles. The eyes are not distinct. 



D. stitnoiiis, Hermann, is about seven lines long. Theleg.s are only seen when the animal is re- 

 versed. It [is found upon the Sturgeon], into the skin of -which it insinuates itself deeply. Hermann 

 found as many as twelve on one fish. Two or three of this number, males probably, were one-third 

 shorter than the others. They twist themselves about with great rapidity. Tliey alltx themselves 

 very firmly by their frontal claws. 



Ntcothoc, Aud. and INI. Edwards, terminates the class of the Cnistacea, and is distinguished 

 by its anomalous form. AVith the naked eye, it appears to consist only of two large lobes 

 united together, somewhat like a horse-shoe, inclosing two others ; but, with the microscope, it 

 appears that the two large lobes are two large lateral expansions of the thorax, having the appear- 

 ance of wings, nearly oval, and directed backwai'ds, and that the two others are external ovaries, 

 like those of the female Cyclops, attached by a small peduncle to the base of the abdomen. The 

 body consists of, 1, a distinct head, supporting two eyes widely apart ; two short, lateral, seta- 

 ceous, ll-jointed antennae ; the month formed of a circular opening, performing the olfice of a cup, 

 accomjianied, on each side, by maxilla-shaped ajipendages (fore-legs); 2, a thorax, composed of 

 four segments, having, on the under-side, five pairs of legs, the two anterior terminated by a strong 

 i^suoL''8ru'"rioDfa hoolc, and the eight others composed of a large joint, terminated by two nearly cylindrical, sub- 

 equal branches, each composed of three joints ; and, 3, an abdonren, pointed behind, composed 

 of five joints, the first largest, and supporting the pair of large, oviparous sacs, the last terminated by two long 

 bristles. The lateral expansions appeal' to be only the excessive developement of the fourth aud last £eg;nieut5 af 

 the thorax. 



N, mtaci (Aud. and M. Edwaids, Ann. .Sri. AVf/. 1S20) is half a line long, and about three lines wide, incloding 

 the thoracic prolongations. It is of a rosy hue, with the lateral expansions yellowish. It attaches itself firmly to 

 the branchi;e of the lobster, burying itself deeply in the filaments of these organs. They occur in small quantities, 

 and only upon certain individuals. All the specimens hitherto obsen'ed were furnished with these ovaries. It is 

 probable, however, that, previous to becoming fixed, they are able to swim ; and tliat, at that period, their thoracic 

 lobes had not acquired their ordinary developement. 



[The aniuiuls composing the Si[)]ioiiostoma are, coniparatively speaking, the iitost impcrfeetly 

 organized of all the Crustaeea; a ])eeuliarity i)rol)aljly resulting, at least to a certain degree, 

 from their parasitic habits. Latreille, in his introductory observations, had noticed the rela- 

 tion of some of these animals with the Lcrnjefc, but doubted the existence of any actual atlinitv 

 between them. Two Prussian naturalists, however, Dr. A'on Nordmann, and my friend Bur- 

 meister, have more reci-'ntly published some elaborate memoirs upon these animals, ^^hieh 

 completely prove theii relation: this is especially the case with sueh genera as AcldJieres, 

 Ergasilas, &c., whieh have nut only articulated bodies and jointed members, but their young 

 are active animals, very closely resembling the young of many of the more imperfect Bran- 

 chiopoda. Dr. Burmeister, whose memoirs are published in the 17th volume of the Noca 

 Acta Cff's. Nat. Curios., accordingly unites these together into one group, ivhicb he calls 

 Schmarotzerkrehse [Siplionostoma, Latr,) divided into five fauiilies : 1, Penellina, com- 

 prising the genera Lcn/cea, Lerna-ocera, Pcnicn/iis, ■.\}\i\ PcnrNa j 2, Lekn.eoda, genera, 

 AnchorfJJa, TrrfchfUfisfes, Brnchielhi, Lenucoj/iu/n, Arlil licrcy., B.'sm/is/i-s, Coiiih^ocnnthus, and 

 Jjcnifiii/hrnp/is j J_|, Ergasilina, genera, K/co/ho/\ Er(/ns/his\ Jhiiiiolorhns, Jjfrmj)ro''/Iene, 

 Anihosorna, Dechelesfium. Neiiie.sis ; 4, Caligina, genera, Cecrops, C//'i/ii,n/s\ Cufnju.s, Pan- 

 darus, and Dinematura j 5, Argulina, consisting of the single geni\s Anjuliis.-'-^ 



:; from g'u-itiK un account I Uvo of Lhu qriiU auimal bubMrii;iliiiMs, M.Kull^ir li.is al^.o I'lihli^liccJ 



