Land, Fresh- Water, and Marine Crustacea. 177 



Family Holopedid^e. 

 Genus (4) Holopedium, Zaddach, 1855. 



4. Holopedium gibberum, Zaddach. 



1855. Holopedium gibberum, Zaddach, Wiegmann, Archiv. fur 

 Naturges., Bd. 21, p. 159, pi. viii. fig. 9. 



Habitat. — Loch Achray, Loch Voil. Common in Loch 

 Achray in September 1897 and June 1898, but entirely 

 absent during the intervening winter months. 



Tribe Anomopoda, G. 0. Sars. 



Family Daphniad^e, Strauss. 



Genus (5) Daphnia, 0. F. Mtiller, 1785. 



The study of the various forms comprised in the genus 

 Daphnia is extremely interesting, but very perplexing. The 

 variations, especially in form, and also to some extent in 

 structural details, are so great that the student of sanguine 

 temperament could easily describe a dozen species where the 

 severely critical could only make out two or three. As I 

 cannot lay claim to a very expert knowledge of the relation- 

 ships of this difficult genus, it is necessary for me to rely, to 

 some extent, on the discrimination of writers more familiar 

 with it. 



5. Daphnia pulex (De Geer). 



1778. Monoculus pulex, De Geer, Mem. pour, servir a l'hist. nat. des 

 Insectes, T. vii. p. 442, pi. 27, figs. 1-8. 



Habitat. — Generally distributed, and occurring sometimes 

 in considerable abundance. Very plentiful in an artificial 

 pond in the vicinity of Edinburgh in July 1898. 1 The 

 variety hamata (Brady) has been taken by Dr and Miss 

 Sprague in Granton Quarry, near Edinburgh, and I have 

 found it, as well as the variety obtusata, in the " marl-pit " 

 near Davidson's Mains, Midlothian. This species possesses 

 a comb-like fringe of minute hairs at the base of the post- 

 abdominal claw. 



1 Seventeenth Fishery Board Report, part iii. (1899) p. 199. 

 VOL. XVI. It 



