52 Zoological Society. 



think erroneously) as identical with the Daphnia yiyas of Hermann. 

 Of this species he formed his genus Litnnadia, and at the same time 

 entered fully into the details of the structure and habits of the ani- 

 mal. In the ' Bulletin de la Societe Imperiale des Nat. de Moscou ' 

 for 1830, M. Krynicki has described a third species belonging to the 

 family, which he found in Russia. M. Audouin, in the ' Annales de 

 la Societe Entomologique ' for 1837, announced to the Society that 

 he had received specimens of another species of the same family, 

 found by M. Bravais, a naval officer, near Oran on the coast of Africa, 

 in a little marsh of brackish water ; and in the same year M. Straus 

 Durckheim published a description and good figure of a fifth species 

 found by Dr. Riippell in Abyssinia. M. Gue'rin-Meneville, in the 

 * Magazin Zoologique ' for the same year, 1837, has published the 

 description of a sixth species brought from the Mauritius, collected 

 there by M. Desjardins ; and finally, M. Joly, in the 'Annales des 

 Sciences Naturelles,' 2nd series, vol. xviii. 1843, has published an 

 elaborate memoir upon a species collected by him at Toulouse. 



From a careful examination of the figures and descriptions given 

 by these authors, it is evident that these animals do not belong all to 

 the same genus. It is perhaps in vain now to attempt to ascertain 

 the species mentioned above as described by Linnaeus. Hermann 

 says, the animal described by him "is very likely to be in reality the 

 Monocuhis lenticularis of Linnseus;" and upon examining the Lin- 

 nsean cabinet in the possession of the Linntean Society, I have found 

 one mutilated specimen of a species belonging to this family which 

 bears much resemblance to that figured by M. Hermann. As there is 

 no ticket attached to the specimen, it is impossible now to decide whe- 

 ther this is really the individual originally in the possession of Lin- 

 naeus ; but if it be, it confirms my opinion, derived from comparing the 

 figures and descriptions of the two species given by Hermann and 

 Brongniart, that the latter author is decidedly in error in considering 

 them to be identical. The species found at Fontainebleau is the true 

 representative of the genus Limnadia, whilst that of Strasbourg forms 

 the type of another genus. This genus was indicated by Audouin 

 and Straus Durckheim in the same year ; the former proposing for 

 the species brought by M. Bravais from Oran, the name o^ Cysicus; 

 and the latter for that broiight by Dr. Riippell from Abyssinia, the 

 generic name Estheria. From the simultaneous publication of these 

 two generic names, it is difficult to decide which should stand ; and 

 M. Joly, apparently feeling the difficulty, has proposed a third name, 

 taking as the type the species found by him at Toulouse, and calling 

 it Isaura. As M. Audouin merely indicates the genus without 

 giving a description of either genus or species, whilst M. Straus de- 

 tails at full length both generic and specific characters, and figures 

 the typical species, I propose adopting his name and retaining the 

 generic name Estkerio, a name originally proposed by Dr. Riippell 

 himself. 



The genus Limnadia thus at present contains two species : — 



1 . Limnadia Hermanni of Ad. Brongniart. 



2. lAmnadia Muuritiana of M, Guerin. 



