1 8 G. (>. SARS. M.-N. Kl. 



The ova in the matrix are, in individuals of the earlier generations, 

 (see fig. i) rather numerous, and of a pale greenish colour, with a large 

 central oil-globule. In specimens of later generations their number becomes 

 much more restricted. 



The ephippium (fig. 6) exhibits the usual structure, being triangular 

 •in form, and containing but a single egg-ampulla placed longitudinally. 



The adult male (fig. 7) is very small, not even attaining a length 

 'of I mm. It differs, moreover, from the female, in the carapace being 

 narrower, and gradually widening behind, with the posterior prominence 

 less projecting, and not defined, above, by any sinus. The dorsal margin 

 appears nearly straight, whereas the inferior edges are slightly sinuated in 

 front of the middle. The head is comparatively larger than in the female, 

 with the frontal part more obtuse. 



The antennulæ are more fully developed, and have each two sensory 

 bristles, instead of a single one, anteriorly. 



The ist pair of legs are each armed with a distinct, though rather 

 small claw, and the terminal jxirt of the tail ajipears narrower, with the 

 posterior edge straight. 



The testes are very conspicuous, forming 2 rather large, and some- 

 what twisted bags extending along the sides of the alimentary tube, and 

 debouching within the anal sinus of the tail. 



The colour of the female is yellowish or ochraceous, turning on the 

 back, and along the ventral edge of the carapace, to pale chestnut; that 

 of the male is much paler, the l)ody being in most cases nearly colourless. 



Observations. This form developed in considerable numbers in 

 several of mv aquaria, and multiplied during the season in quite an 

 astonishing manner, so as to cause the aquaria literally to swarm at last, 

 with individuals in different stages of development. Contrary to what is 

 o-eneraUy the case, male specimens occurred at the close of the season in 

 innumerable shoals. In habits this form exactly agrees with the other 

 known species. 



Fam. : Lynceidse. 



Gen. : Leydigia, Kurz. 



7. Leydigia acantiiocercoides, (Fischer). 



(PI. 4, figs. 1—4). 



Lyncciis acanthoccrcoidcs, Fischer, Bullet. Soc. Imp. des Natural, de 



Moscou, p. 431, Fl. III, figs. 21—25. 



Specific Characters. Carapace of female, seen laterally, subquadran- 



gular, widening somewhat posteriorly, upper margin forming, together with 



