OCR Text |
Show 118 CRUSTACEA. There, the thorax or the shell, viewed from above, is divided into five segments, of which the fit·st is much the largest and has the an. tennre, eyes, and foot-jaws attached to it; the second and the third have each one pair of feet, the fourth has the two following pairs, and the fifth, the last. The eyes are small and not prominent; all the antennre are terminated by a single tlueacl. CoNnYLURA, Lat. The inferio1· antennre longest; the anterior sides of the first sep· ment prolonged into a point forming two scales approximated into a kind of rostrum; feet terminating in a silky point; some of the intermediaries, as in the Schizopoda, with an external appendage near their base; the tail narrow and formed of seven annuli, the last of which, conical and elongated, projects between the two lateral appendages that are slender, styliform, and composed of two joints, the last silky( 1 ). We should remark, that the genus Nicotltoe of MM. Audouin and Milne Edwat'ds, by admitting it to have mandibles and jaws, would belong to this s~ction; but as the animal on which it is founded is parasitical, and, as I think I perceived in it a vestige of a sucker, 1 have placed it among the Precilopoda. I would observe, however, that the feet, the anterior excepted, closely resemble those of Cyclops, and that the females also carry their ova in two sacs situated at the base of the tail as in the latter genus(2). a rostrum articulated at base, or movable and pointed; the eyes are pedunculated· the sup.erior ~ntenn~ are ins:rted under them, and the second joint of their pe: duncle uifurn.Ished With a lamtna; the mouth is surrounded with three pairs of ap· p~ndages wl11c.h appear to u~ to c01·respond in their progressive order to the pal. p1gero~s mand1~les and four ~~ws of the Crustacea Decapoda; beneath are placed five pa1rs of foliaceous and ciliated lamina: which appear to be branchial, and fur. ther down ~re four pairs o~ bifid and natatory feet; the abdomen is composed of seve~ annul1, the first of whtch support two small rudimental filaments; the last is termmated by two e.longated sty lets furnished with long hairs. As it is extremely probable that there Is, as usual, another pair of feet, the two inferior and branchial appendages above mentioned, may very well represent that pair. In the other appen.dages we should find foot.jaws and the parts of the ligula; in that case the N ebal1a: must be referred to the last section of the Decapoda :.Macroura. (1) Condylura Dorbigni, Lat. }'rom the sea coast of Hochelle. (2) Near the Condylura: should be placed the genus Cu:11u., M. Edwards Ann. des Sc. Nat. Xlll, xiii, B. The superior antenna: are rudimental and co~sist of but one joint. The hea~ is distinct from the thorax which is divided into fourscg· ments, to the first of wb1ch are attached the four anterior feet each of the follow· ing having a pair; all these feet are natatory, directed forward:, and have no hook at the end; the two fiJ·11t pairs alone are bifid. BRANCHlOPODA. 119 · 'ng Lophyropa of our first division, the thorax, as I 0 the redm a1m t f h' h 1·s divided into several segments, the first o w tc · the Con r ura, f 10 h 1 gest· they have but one eye situated in the centre o is much t e ar ' . th f t between the superior antennre. Such IS e the ron CYcLoPs, Mull., S ell studied by Jurine, Sen., and Randohr. The bod~ is more 0 w 1 soft or gelatinous, and divided into two portiOns, one or less ova , . · m}>osed of the head and thorax, the other postertor, or anterior, co . 1 'I The segment immediately precedmg the sexua organs, the tal· · · 1 d · the d h. h 1 • 0 the female, is provided Wit 1 two appen ages In · an w lC ' • fi f I'ttle feet-fulcra, Jurine-may be considered as the rst form o 1 J , d d I d. . . h d of the tail, which is not always decidedly or su en y tstmguts e from the thorax. It is composed of six parts or segments; ~nder ~he d · the males are two articulated appendages, sometimes stm-secon m ' . . . I d t others with a small hranch on the mner s1de of yar1ous p e, an a . 1 f forms, and constituting, either wholly or 'partial y, the organs o gene- . The vulva in the other sex, is situated on the same segment. ration. ' t · f k The last one is terminated by two points or sty!ets, orm1ng a or , and is more or less furnished with setre or penmform threads. The other or anterior portion of the body is divided into four segments, the first of which is much the largest, and composes the head and part of the thorax, which are also covered by a c?mmon seal~. In it, are inserted the eye, four ant~nnre, two man.dlbles~mandtbule.s intel'nes of Jurine, furnished with a palpus, either stmple or dtvided into two articulated branches, two jaws-manuibules externe~, or levre avec des barbillons of J urine( 1 ), and four. feet, each di- 'd d · to four cylindrical stems furnished with hairs or bearded VI e 1D h d • d'ffi threads; the anterior pair, corresponding to t e secon Jaws, . 1 ers slightly from those that follow. Jurine compares it to a kmd of The genus PoNTIA, Jd., lb., XIV, appears to us to approac.h ~yclops. The head is distinct from the trunk, and terminated by a rostrum wh1ch IS rather acute and appears to be formed of two pieces; it bas two sessile .e!es; four a~tem~a:, the superior of which are setaceous, multi-articulated and c1ha~e~;. the mfer1or are pediform, composed of a peduncle, serving as a base to t~o divlSIO~s. or branches, each terminated by a pencil of hairs, one of them havmg two J?mt.s,. the .]ast widened at the end, and the other consisting of one. The thorax IS dt~tded mto five annuli, and has six pairs of natatory and bifid feet. The abdomen IS formed of two segments and terminated by two spatula-like appendages or fi~s. , (1) According to the successive order of the parts o~ the. mouth. m the Decapoda, the part situated immediately beneath the mandibles IS the 1Jgu1~; but the dentation of those here spoken of indicates maxillary organs .• The hgula may have escaped the notice of 'M. Jurine. |