178 Geographical Distribution of the G^enus Diaptomus. 



The remainder — that is to say, D. castor , Jurine, D. cwruleus, 

 O. F. MiilL, D. denticornis, Wierz., D. gracilis, G. O. Sars, 

 D. graciloides, Lillj., and D. laticeps, G. 0. Sars — are more or 

 less diffused in the north, east, and west of Europe. 



In France and in the British Isles we only know D. castor 

 and D. cwruleus, which are also noted in Sweden and Ger- 

 many. D. cceruleus lives in numerous troops in clear waters 

 of a certain extent ; D. castor, on the contrary, is met with 

 in small pools or in the littoral region of lakes. D. gracilis 

 occurs throughout northern and central Europe ; it is the most 

 widely diffused of the lacustrine forms ; an allied species, D. 

 graciloides, is met with throughout Sweden and into Russian 

 Lapland (Lilljeborg). D. denticornis is known in Scandi- 

 navia, in Switzerland, and in the Tatra mountains. D. lati- 

 ceps, indicated in Finland * and in Norway, has been recog- 

 nized by S. A. Poppe in the Salzigersee, near Halle on the 

 Saale. 



In Asia, at points very distant from each other (Beliring 

 Island, Turkestan, Shanghai, Ceylon, and Jerusalem), we 

 know six species of Diaptomus. It is certain that future 

 researches will lead to the discovery in this country of a 

 great number of other forms, and this is the more probable 

 because, except as regards Turkestan, the types at present 

 noted have been met with at a short distance from the coasts. 



Scarcely any investigations have been made in Africa ; and 

 the only two Diaptomi brought from that continent are new. 

 Both come from Algeria. One was collected near Algiers by 

 M. Letourneux ; the other, discovered in the neighbourhood 

 of Oran by M. Raphael Blanchard, has also been found by 

 him at Temacin, to the south of Tougourt. 



In America the Diaptomi have been the object of only a 

 few researches in the United States. Among many ill-defined 

 species we may distinguish five, which certainly do not 

 represent the whole richness of the genus in that country f. 



South America has hitherto furnished only one well-recog- 

 nizable Diaptomus ; another species, brought from Patagonia 

 by Charles Darwin, indicates the extension of the genus into 

 the southern regions. 



Moreover four species noted in Oceania lead us to suppose 

 that the genus is largely represented in the southern hemi- 



* It is a mistake, in our opinion, for Dr. O. Nordqvist to unite D. lati- 

 ceps with D. gracilis (" Die Calaniden Finlands/' in Bidr. till Kanned. af 

 Fiul. Nat. och Folk, part 47, p. 7, note 3). 



+ Under the name of castor Bucholz has indicated a Diaptomus col- 

 lected in East Greenland in February 1870, the determination of which 

 appears doubtful to us. 



