ORDER BRANCHIOPODA. 333 



while the lower, on the contrary, present more ; also by rea- 

 son of its body, which gradually grows slender towards its 

 posterior extremity, so that it appears to have no tail, at least 

 abruptly formed, and its under part is armed, in the female, ' 

 w4th a sort of horn, curved backwards. The cy clops castor, 

 and some others, whose lower antennee and mandibulary 

 palpi are divided beyond their base into two branches, may 

 also compose another group. That which Dr. Leach desig- 

 nates under the generic name of Calanus, might, indeed, 

 form a subgenus proper, if it were true that the animal of 

 which it is the type had no inferior antennae. But has he 

 ascertained this point himself, or does he speak of it only after 

 Miiller ? This I know^ not. 



Cyclops quadricornis, Monoculus qiiadricornis, Linn., 

 Mull., Entom. xviii. 1 — 14; Jurine. Monoc. i. ii. iii., has all 

 the antennas simple, or without divisions. The lower have 

 four articulations, and their length scarcely equals the third 

 of the upper ; the body properly so called is tolerably inflated, 

 and almost ovoid ; the tail is narrow, and composed of six 

 segments. The colour varies much ; some are reddish, others 

 whitish or greenish. The total length is two lines. This 

 species is very common. — Desmarets' Consid. p. 364. See, 

 for the other species, the same work, p. 361 — 364; MiilL 

 Entom. G. cyclops, Jurine Hist, des Monoc. p. 1 — 84, first 

 family of the Monoculi with univalve shell, Ramd. Monoc. 

 i. ii. iii. 



The second general division of the branchiopodous lophy- 

 ropa, those whose testa is formed of two valves, united by a 

 hinge (our Ostracoda, or the order of Ostrapoda of M. 

 Straus), is composed of two subgenera, the first of which, that 

 of Cytherea, appears to us, since the valuable researches of 

 this naturalist on the second (cypris), to require, for the pur- 

 pose of establishing its characters in a less equivocal manner, 



