FRESH-WATER CYCLOPID.E AND CALANIDJE. 29 



joint of the outer branch : just above the origin of this branch, 

 the margin of the protopodite is produced in the form of a 

 hyaline lamina : the outer branch consists of three joints, the 

 penultimate strongly angulated near the middle, to which is 

 attached a rather long and stout seta ; last joint simple, slender, 

 and forming a long, falcate claw : inner branch of the left side 

 simple, two-jointed, and about as long as the outer branch ; 

 terminal joint of the outer branch subglobose, ending in two 

 short, sharp processes, between which there is a crenulated, disc- 

 like surface; inner margin of the joint setiferous. Length of 

 the female, 2*5 mm. {circa) ; of the male, 2 mm. {circa). 



Diaptomus Castor is recorded by almost all European writers 

 on the Copepoda, and though it is mentioned by Herrick in his 

 memoir on the Crustacea of Minnesota, it does not appear that 

 the genus has been examined by American authors with suffi- 

 cient precision, so that it is uncertain as yet whether this 

 species occurs on the American continent. In Scandinavia its 

 occurrence is noted by Muller and Lilljeborg, in Germany by 

 Poppe and others ; in France by De Guerne and Richard, in 

 Bohemia by Trie, in Switzerland by Jurine. In our own country 

 it seems to be generally distributed, though by no means a very 

 common species ; very rarely occurring in lakes or large sheets 

 of water, but generally in ponds or ditches where there is much 

 vegetation. My notes embrace the following localities: — Ponds 

 at Chester Road, Sunderland ; Shotton, and Wardley, county 

 Durham {G. S. B.); Eroomley Lough, Northumberland {Rev. 

 Dr. Norman); ponds in Wanstead Park and at Pavenham, 

 Bedfordshire {Mr. I). J. Scourfield). Dr. Baird records it as 

 being "common in the neighbourhood of London." 



2. Diaptomus gracilis, G. 0. Sars (PI. XL, figs. 7-9 ; 



pi. XIL, figs. 1-8). 



1863. Diaptomus gracilis, Sars (20), p. 9. 



1863. ,, 7F^w;o^V,Lubbock(19),p.203,pl.XXXI., 



figs. 1-6. 

 1888. ,, ,, Nordquist (51), p. 71, pi. IX., 



figs. 1-7. 

 1888. ,, graciloides, Lilljeborg (53), p. 156. 



94 



