12 G. O. Sårs. 



was procured from the very same region; but a closer 

 comparison of the figures of the shell he gives, seems to 

 forbid such an identification. In Baird's species the shell 

 is almost twice as large, and is not nearly as narrow as in 

 the present form. It has, moreover, a much greater number 

 of lines of growth, and the same is also the case with the 

 second South African species he describes as Estheria Ru- 

 bidgei, though it does not exceed the present species in size. 

 It is also worthy of note, that the first-named species was 

 procured from a salt-lake, whereas the present species is a 

 true fresh — water form. In the shape of the shell, it bears 

 a much greater resemblance to the North American form, 

 Estheria compleximana of Packard; but it is not easy to 

 believe that these 2 forms can be identical, occurring as 

 they do in such widely distant localities. The specific name 

 here proposed is derived from the very narrow compressed 

 shape of the shell somewhat reminding of that of a little 

 legume. 



Description. — The length of the shell in adult, ovi- 

 gerous females is about 6 mm., by a height of 3 mm. In 

 the male the shell reaches a length of 7 mm., and this 

 seems endeed to be the maximum size of the present 

 species. 



In shape, the shell of female and male specimens 

 scarcely exhibits any pronounced difference. Seen laterally 

 (PI. 2, figs. 1 & 2), it has a narrow oblong form, with the 

 greatest height scarcely exceeding half the length. The 

 umbones are very small, and form a rather slight prominence 

 above, at a short distance from the anterior extremity. 

 Otherwise the dorsal margin is perfectly straight and hori- 

 zontal, joining the free edges of the valves by a very slight 

 angle both in front and behind. The ventral margin forms 



