ON BOSMINID,E, MA.CEOTHEICID.ffi, ETC. 371 



structure, while variations of form more properly constitute spe- 

 cific character. The discovery of many intermediate species since 

 1843 has clearly proved, either that the genus Lynceus, if form 

 of carapace alone be relied on, must be divided into almost as 

 many genera as there are species, and that thus the process of 

 multiplication of genera must be carried further, as has been 

 done by G. 0. Sars and Schoedler, or the several genera enume- 

 rated above must be merged in Lynceus, as has been done by 

 Lilljeborg and Leydig. We believe the latter to be the right 

 course. Lynceus is a natural group, distinguished from its allies 

 by structural characters. If the reader will cast his eye over 

 the synonymy of the following pages, he will at once see the 

 difficulties under which authors have laboured in their attempts 

 to allocate the several species in the unsatisfactory genera which 

 have been established. We will merely here call attention to 

 two, out of many instances, in proof of this. Lynceus tenuicaudis 

 is so exactly intermediate between Alona and Camptocercus, that 

 Schoedler at first called it Camptocercus alonoicles, and subse- 

 quently changing his mind, dubbed it instead Alona camptocer- 

 coides. The poor little Acroperus nanus of Baird has found no 

 resting place : while Lilljeborg and Leydig, rightly as we think, 

 unite it with all its allies in Miiller's genus Lynceus, Baird 

 places it in Acroperus, Schoedler in Pleuroxus, Gr. 0. Sars in 

 Alona, and the same author in his later paper in Alonella. 



Although however we have thought it better at the present 

 time to unite, under the name of Lynceus, the species about to be 

 described, it is not improbable that a more thorough examination 

 of the structure of the animals than has yet been made may here- 

 after result in the establishment of genera upon a satisfactory 

 basis, in which case some of the genera now suppressed might 

 be adopted with re-defined characters. 



•1 . Lynceus HAEPiE, Laird. PL XXI, fig. 1 . 



1835. Lynceus harpce, Baird. Trans. Berw. Nat. Club, Vol. I, 



p. 100. PI. II, fig. 17. 

 1841. Lynceus leucocephalus, Koch. Deutschlands Crustaceen, 



Myriapoden u Arachniden, p. 36. PL X. 



