290 Transactions of the Society. 



The species here described appears to be very closely related 

 to Moina micrura Kurz. The general form of the body and of the 

 post-abdomen are the same, but M. salinarum differs from it in 

 being considerably larger, in having more teeth on the post- 

 abdomen, and in having the claws of the post-abdomen armed 

 with denticles, whereas they are smooth in M. micrura. These 

 differences are not such as might be caused by adaptation to life 

 in water of high salinity, since such adaptations usually take the 

 form of reduction and simplification of parts. I believe, therefore, 

 that the species is distinct, though it is much to be regretted that 

 the male and ephippial female are not available to put the matter 

 beyond doubt. 



Moina rectirostris Jur. — Apparently rather a common species 

 in the neighbourhood of Tunis, being found at Sidi Athman, Oued 

 Tindja and Eades. There is no doubt that my specimens belong 

 to this species, though they differ in some minute points from 

 specimens taken in England. In all essentials the agreement is 

 exact. The only striking point of difference is the presence of 

 seven hooks on the first antenna of the male instead of the normal 

 number of five. The difference is remarkable since the number 

 of sensory setre and other outgrowths of the first antenna of 

 Cladocera is not as a rule subject to variation.* 



Macrothrix hirsuticomis Norman and Brady. — This is the com- 

 monest of all the Cladocera found in Algeria and Tunisia, being 

 met with in nearly every pool in Biskra and its neighbourhood, 

 and also in various places near Tunis. As is frecpuently the case 

 among the Macrothricichv, this species seems very rarely to repro- 

 duce by means of resting-eggs, although it inhabits, in Biskra, at 

 all events, pools of water which become dry periodically at short 

 intervals. If resting-eggs are not produced in these circumstances 

 it seems almost incredible that the species should be able to per- 

 sist. And yet I met with ephippial females in only one of the 

 irrigation pools examined. Males and ephippial females were 

 found in shallow flood-water covering a road at Sidi Athman near 

 Tunis and in a roadside ditch at Hades. Lilljeborg (1900) states 

 that the male and ephippial female are unknown. 



The male is much smaller than the female, measuring 0*35 to- 

 0-5 mm. The head is very large, rather more than one -third the 

 length of the whole body (plate X. fig. 16). In general shape 

 it is more or less rectangular, the dorsal and ventral margins of 

 the shell-valves nearly straight, the posterior margin forming a 

 rounded angle with the dorsal margin. The eye is not larger than 

 that of the female. The first pah- of antennas are nearly as long- 

 as the head, curved, and not dilated at their extremities (plate XL 



* See Scourfield, The Olfactory Setae of the Cladocera, Journ. Quekett Micr. 

 Club, ii. vi. 1896. Die sogenannteu Riechstabchen der Cladoceren, Ploner For- 

 schungsberichte, xii. 1905. 



