396 REV. A. M. NORMAN AND ME. G. S. BRADY 



the Crustacea which live in it. It often happens, that in the 

 same spot which at one visit has produced a species in the greatest 

 profusion, on the next not one can be found. This has occurred 

 to us in the present instance ; for on a subsequent visit to Belsay 

 Lake, undertaken at a somewhat earlier period of the year, not 

 one of these interesting species was taken, but we were rewarded 

 by the capture of some remarkable Ostracoda. Xo doubt such 

 fluctuations in the appearance of species of Entomostraca is de- 

 pendent, in no slight degree, upon the different conditions under 

 which our search is conducted, and that the exact season of the 

 year, the time of day, the force and direction of the wind, the 

 degree of sunlight and sunshine, and the variations in tempera- 

 ture, must all be taken into account ; but no one of these secon- 

 dary causes, nor all of them taken together, seem sufficient to 

 account for the capriciousness which, in our experience, has cha- 

 racterized the appearance and disappearance of certain species of 

 the smaller Crustacea in particular localities. 



18. Lynceus nanus, {Baird). PL XVIII, fig. 8; and PI. 

 XXI, fig. 8. 



1843. Acroperus nanus, Baird. Ann. and Mag. Nat. Hist., 

 Vol. II, p. 92. PL III, fig. 8. 



1850. Acroperus nanus, Baird. Xat. Hist. Brit. Entom., p. 130. 

 PL XVI, fig. 6. 



1853. Lynceus nanus, Lilljeborg. De Crust, ex Ord. tribus 

 Clad. Ostra. et Copep., p. 206. 



1860. Lynceus nanus, Leydig. Naturgeschichte der Daphniden, 



p. 228. 



1861. Alona pygmcea, Gr. 0. Sars. Om de i Omeg. af Christ. 



forekom. Cladocerer, p. 21. 



1862. Ahnella pygmcea, G. O. Sars. Om de i Omeg. af Christ. 



forekom. Cladocerer. Andet Bidrag., p. 48. 



1863. Acroperus nanus, Schoedler. Xeue Beitrage zur Xaturg. 



der Cladoceren, p. 33. 



