154 CRUSTACEA. 



Nicothoe, Aud. and Edw. 



These animals terminate the Crustacea, and are distinguished from 

 all others of that class by their heteroclitical form. To the naked 

 eye they seem nothing more than two lobes united in the form of a 

 horse-shoe, which enclose two others. By the aid of glasses, how- 

 ever, we discover that the two large lobes are formed by the great 

 expansion of the sides of the thorax, which resemble wings, are 

 almost oval and thrown behind ; that the two others are external 

 ovaries or clusters of eggs, analogous to those of a female Cyclops, 

 and inserted, one on each side, into the base of the abdomen by 

 means of a short pedicle; and that the body of the animal is com- 

 posed of the following parts: 1, a distinct head furnished with two 

 separate eyes; two short, setaceous, lateral antennae formed of ele- 

 ven joints, each with a hair on the inner side; a mouth forming a 

 circular aperture which acts as a cup, and accompanied on each side 

 with anterior feet maxilliform appendages; 2, a thorax of four 

 segments, with five pairs of feet beneath, the two anterior of which 

 are terminated by a stout hook, and are bidentated on the inner side; 

 the remaining eight being formed of one large joint, terminated by 

 two nearly equal and cylindrical stems, each composed of three 

 joints, and furnished with setae: 3, a pointed abdomen of five annuli, 

 the first and largest of which gives origin to the oviferous sacs; the 

 last is terminated by two long hairs. The lateral expansion merely 

 appears to be an excessive development of the fourth and last ring 

 of the thorax. Within we may perceive two kinds of entrails origi- 

 nating from the median line of the body, which may be considered 

 as caeca or divisions of the intestinal canal in a state of hernia. They 

 are endowed with a very decided peristaltic motion. We have seen 

 that the stomach of the Arguli also exhibits two caeca, which ramify 

 in the wings of their shell, and it is possible that these thoracic ex- 

 pansions of the Nicothoes may be two analogous lobes(l). 



Nicothoe astaci, Aud. and Edw. Ann. des Sc. Nat., 1826, 

 XLIX, 1, 9. The only species known; it is about half a line 

 long and three lines broad, the thoracic enlargement included. 

 It is rose-coloured, paler on the oviferous sacs; the expansions 

 yellowish. It adheres closely to the branchiae of the Lobster, 

 and penetrates deeply between the filaments of those organs. It 

 is only found in small numbers, and on a few individuals. All 

 the Nicothoes observed by these two naturalists were furnished 

 with ovaries; it is probable that previously to fixing themselves 



U) In this case, the genus may be approximated to the preceding 1 one. 



