104 . THE ZOOLOGIST. 



Chydorus, Camptocercus, Alona, Pleuroxus, and Peracantha, these, 

 with the genus Acroperus, forming his family Lynceidce. Here 

 it is a little startling to observe that the family Lynceidce is set 

 up, but the genus Lynceus itself is shut out. Also three of the 

 Miillerian species are not accounted for, namely, L. brachyurus, 

 L. longirostris, and L. socors. Of these Baird refers the second 

 to Bosmina, as a genus of the Daphniidce ; the third is perhaps 

 unidentified ; the first remains over for consideration. 



In 1867 Norman and Brady, in their well-known paper on 

 " The Families Bosminidce, Macrothricidce, and Lynceidce," re- 

 assemble, under the title Lynceus, no less than eleven genera, 

 no one of which, however, includes any of the three species 

 omitted by Baird from the family Lynceidce. The principle on 

 which these two authors acted was that for generic distinction 

 structural characters should be insisted on rather than variatiors 

 of form. Though they do not make it very clear how the line is 

 to be drawn between form and structure, there was something t,o 

 be said for their opinion that generic subdivision in the famiy 

 had been carried beyond the point which was justified by aay 

 thoroughness of contemporary knowledge. None the less they 

 recognized the importance of the treatise by G. O. Sars on tie 

 ' Cladocera Ctenopoda,' 1865, and they contemplated the possi- 

 bility that in the future some or all of the rejected names might 

 properly be reinstated. This has come to pass. But authors 

 have still been content to follow Baird in adopting a Cladocerm 

 family Lynceidce, in which no genus Lynceus was included, 

 although of other generic names within that family the number 

 has risen to at least eighteen. At length, however, in lis 

 'Cladocera Suecise ' (1900 or 1901), the veteran zoologst, 

 Wilhelm Lilljeborg, raised a protest against this way of treating 

 O. F. Miiller's genus, and restored it in favour of Lynieus 

 quadrangular is, M tiller, which Baird had transferred in 1845 to 

 a new genus Alona. But, as already explained, the actioi of 

 Leach has affixed the title Lynceus to the species L. brachywus. 

 Accordingly, in any settlement of claims it is to that speies 

 that attention must first be given. It has nothing to do yith 

 Alona, for it is not one of the Cladocera at all. It s a 

 phyllopod, and, as may be seen from the * Fauna Norveise ' 

 of G. 0. Sars (vol. i. p. 116, 1896), in which it is fully desci.bed 



