96 BRITISH ENTOMOSTRACA. 



MoNOCTJLUS siMUS, Gmeliii, Syst. Nat., 13tli edit., i, 3000, No. 25, 

 1788. 



— Manuel, Eucyc. meth., ra, 723, No. 18. 



— Jurine, Hist. Nat. Mouoc, 129, t. 12, f. 1. 

 MoNOCULUs LEVIS, Fabricuis, Eut. Syst., ii, 492, 1793. 

 MoNOCULUS EXSPiNOSDs, De Oeer, Mem. pour servir a I'Hist. Ins., 



Tii,457, t. 27,f. 9-11, 1778. 

 MoNocuLXJS coxcHACEUS, Donovun, Nat. Hist. Brit. lus., i, 15, t. 5,f. 1. 

 Ungeschwanzter-zackiger Wasserfloh, Schaffer, Die griiu. Arm- 

 Polyp., 229, 1. 1, f. 9. 

 MoNOCULUS NASUTUS (?), Jiirine, 1. c, t. 13, f. 1. 

 MoNocuLUS pulex, Sulzer, Abgekurzte Gescliichte der Insecteu, 266, 



t. 30, f. 10 e. 

 Daphnia congener, Koch, Deutscli. Crust., li. xxxv, t. 13. 

 Daphnia EXSPiNOSA, Koch, 1. c, h. xxxv, 1. 11. 



The shell or carapace is ovate, transparent, and smaller 

 than in any of the preceding species. It is striated; the 

 striae being deep, and sometimes crossing, so as to pro- 

 duce a reticulated appearance, especially on the anterior 

 margin, which is furnished with numerous long cilia. The 

 posterior extremity is rounded, slightly serrated, destitute 

 of the spine which marks the preceding species, and is 

 obliquely truncate anteriorly. 



The head is obtuse, much smaller than m pule,T, and 

 the beak less projecting. The superior antennae are 

 larger than in any of the preceding species, consisting of 

 a stout joint, arising from under the beak, and five short 

 setae. The filaments of the large antennae are jointed 

 and plumose, but not so decidedly as in the preceding. 

 The sixth segment of the body has about three small pro- 

 jections from the posterioi' portion ; and near its upper 

 part one longer, like a spur, slightly curved upwards, 

 which serves to hold up, or keep back the ova from falling 

 down beyond a certain distance. 



Hah. — Ponds and ditches round London, &c. ; common 

 throughout the sununer and autumn. Belfast, May 1849, 

 W. Thompson, Esq. 



