On Fresh-water Entomostraca. 73 



small and of a linear form, carrying only 2 apical spines, 

 the inner of which is the longer. Otherwise these legs, as 

 also the other appendages, exhibit the structure charac- 

 teristic of the genus. 



The adult male, as usual, is even somewhat smaller 

 than the female, and differs from it in the usual sexual 

 characters. 



The last pair of legs (fig. 7) are on the whole con- 

 structed as in the other species, though, on a closer com- 

 parison, several minor differences may be found to exist. 

 Thus, the last joint of the outer ramus of the right leg is 

 comparatively narrower than in the preceding species, and 

 on the left leg this ramus is somewhat attenuated distally, 

 whereas in B. robusta it is on the contrary, dilated at the end. 

 The inner ramus in both legs is simple cylindric, being 

 somewhat larger in the right than in the left leg. In the 

 latter, the last joint of the basal part projects inside to a 

 sharp corner, but any serrated lamella, like that found in 

 B. triarticulata, does not exist. 



In the living state of the animal, the body is highly 

 pellucid and almost colourless, admitting of some of the inner 

 organs being pretty easily traced through the thin integu- 

 ments. The ovisac in the female (see fig. 5) only contains 

 a very restricted number of eggs of a pale greenish colour. 



Observations. — Some few specimens of this form 

 developed in one of my aquaria and were watched for 

 about a month. They did not, however, multiply, though 

 some of the females were ovigerous, and in the later part 

 of the summer they wholly disappeared. In habits it agrees 

 with B. triarticulata, moving about in quite a similar manner. 



Occurreuce. — The mud, from which this form deve- 

 loped, was taken by Mr. Whitelegge from a pond off Botany 



