292 Transactions of the Society. 



Pleuroxus aduncus Jurine. — A few specimens found in the 

 fountain basin, and in a tank in the Jardin d'Essai in Algiers. 



Chydorus sphmricus O.F.M. — A rare species, found only at 

 Algiers and Oued Tindja. Its place seems to be taken by the 

 next species. 



Chydorus letourneuxi Eichard. — This species was found in 

 several of the irrigation pools in Biskra, and in pools at Sidi 

 Athman in Tunisia. Males and one ephippial female were among 

 the specimens taken at the latter place. 



The ephippium resembles that of Chydorus barroisi * in that 

 the dorsal chitinous thickening extends up nearly the whole length 

 of the back. The ephippial area is dark and strongly reticulated, 

 with the surface finely punctate, but I am unable to detect a 

 definite line of fracture, and have no knowledge of the shape of 

 the ephippium when shed. There appears to be a crumpled inner 

 membrane enclosing the egg (plate XI. fig. 23). 



The male is much smaller than the female, measuring about 

 0*35 mm. in length and 0*26 mm. in greatest width (plate XL 

 fig. 20). The shape of the shell does not differ much from that of 

 the female, but the ventral margin is rather more prominent. The 

 first antenna is short and thick, with two lateral sensory setse and 

 nine terminal sensory rods (plate XL fig. 21). The prehensile 

 appendage bears a strong, sharply bent claw, which has two minute 

 recurved teeth at its extremity. The anterior edge of the appendage 

 is thickly fringed with cilia arranged in transverse rows. The post- 

 abdomen is similar to that of the female both in shape and in 

 arrangement of the delicate cilia. The ventral edge of the valves 

 is spinous, as in the female, but the spines are not, in either sex, 

 outgrowths of the shell itself. They are really the thickened 

 bases of the setee which fringe the valves (plate XL fig. 22). 



Dunhevcdia crassa King. — There can be no doubt that D. seti- 

 gera Birge is identical with D. crassa King, as Stingelin has shown. 

 The sole important difference between the two species appears to 

 lie in the greater or lesser sculpturing of the shell, the form of the 



* Scourfield, 1902, fig. 35. 



EXPLANATION OF PLATE XII. 



Fig. 24. — Cyclops planus sp. n. Female, x 98. 



„ 25. — Ditto. 5th foot of female, x 540. 



„ 26.— Ditto. 3rd foot, x 260. 



„ 27. — Ditto. 1st antenna, x 260. 



„ 28. — Diaptomus numidicus sp. n. Abdomen of female, x 98. 



,, 29. — Ditto. Rostral processes of female. 



,, 30. — Ditto. Joints 23 and 24 of right antenna of male, x 260. 



,, 31.— Ditto. Female, x 57. 



,, 32.— Ditto. 5th legs of male, x 150. 



