254 CRUSTACEA. 



with an oval shell resembling that of a molluscous bivalve, and the 

 ovaries arc always internal. Such is the 



LIMNADIA, Ad. Brong. * 



The Limnadise are so closely allied to the preceding subgenus, that 

 the only species known was placed among the Daphniae by the 

 younger Hermann. The shell is bivalve, oval, and incloses the body, 

 which is elongated, linear, and inflected forwards. In the head, and 

 almost confounded with it, we find : 1, two eyes closely approxi- 

 mated and placed transversely ; 2, foar antennae, two of which are 

 much the largest, each composed of a peduncle of eight joints and 

 of two setaceous branches or threads divided into eight segments and 

 somewhat silky; the two others are intermediate, small, simple, and 

 widened at base; 3, the mouth, situated beneath, and consisting of 

 two inflated mandibles arcuated and truncated at the inferior extre- 

 mity, and of two foliaceous jaws. These parts, when united, form a 

 sort of inferior rostrum. The body, properly so called, is divided into 

 twenty-three segments, each of which, except the last, bears a pair of 

 branchial feet. All these feet are similar, strongly compressed, and 

 bifid ; their external division is simple, and ciliated on the exterior 

 edge; the other has four joints, and is strongly ciliated along its inte- 

 rior margin. The first twelve pairs are of equal length, and larger 

 than the others; the length of the latter progressively diminishes. 

 The eleventh pair, and the two following ones, have a slender 

 thread at their base, which ascends into the cavity situated between 

 the back and the shell, in order to support the ova. The last seg- 

 ment on the tail is terminated by two threads. The ovaries are 

 internal, and placed along the sides of the intestinal canal, extending 

 from the base of the first pair of feet to the eighteenth ; their open- 

 ings appear to be at the root of some of those that are intermediate ; 

 the eggs, after having been produced, occupy the dorsal cavity above 

 mentioned, and are secured there by means of small threads, which 

 adhere to those of the feet. At first they are round and transparent; 

 they afterwards assume a yellowish tint, which is subsequently darker 

 towards the centre, and their figure becomes irregular and angular. 



All the individuals examined by M. Ad. Brongniart were provided 

 with them. The males, allowing the sex to exist, do not appear at 

 the same time as the females, which is during the month of June, and 

 are unknown. 



Limnadia Hermani, Ad. Brongn., Mem. du Mus. d'Hist. 



Nat., VI, xiii; Daphnia-gigas, Herm., Mem. Apterol., V. 



Found in great numbers in the little pools of the forest of Fon- 



tainebleau. 



There, each eye is situated at the extremity of a pedicle, formed by 

 a lateral prolongation, in the shape of a horn, of each side of the head. 

 The body is naked, without a shell, and annulated throughout. The 



* In my work on the natural families of the animal kingdom, this subgenus, with 

 that of Apus, composes my family of the Aspidiphora ; it approximates to this one 

 in the number of feet, and to the Daphnia- in the shell. 



