D. J. SCOURFIELD ON EPHIPPIA OF LYNCEID ENTOMOSTRACA. 229 



sometimes rather less. It exhibits several interesting features. 

 In the first place, the whole of the ventral third of the shell splits 

 away from the remaining portion, the line of separation being 

 continued straight to the posterior margin, and not running off to 

 meet the ventral margin, as is usually the case (see Fig. 16). 

 In the drawing the ephippium is shown with the ventral parts of 

 the valves still attached. These and other ephippia, as already 

 seen in the case of A. costata, are very often found in this con- 

 dition, but they are also found without the ventral parts of the 

 original shell. It probably depends to some extent upon the 

 usage to which they have been subjected after being thrown 

 off by the animal. 



Another peculiarity is to be found in the elaboration of the 

 inner membranes surrounding the egg into a delicate cellular 

 '* packing," not so well marked nor so copious as in Alonopsis 

 umhigua and Alona tenuicaudis, but apparently representing a 

 step in the same direction. The coarser structure is fairly well 

 shown in Fig. 16, where it will be seen that, closely investing the 

 egg and extending from the back almost to the other three edges 

 of the ephippium, there is a mass of irregularly polyhedral cells 

 having somewhat ragged margins. In each of these larger cells 

 there are a great many smaller ones, the iiTegular edges of which, 

 seen in optical section, produce the impression of a cavity filled 

 with fine spider lines (see Fig. 17). This ephippium is very dark 

 brown, almost black, in colour, and the darkening occupies 

 approximately the same area as the "packing." The dorsal 

 margin is thickened as usual, and the line of weakness is 

 produced by the formation of a special chain of loosely adhering 

 chitinous plates, as may be inferred from the few still attached 

 in their places to the edges of the crack. The ordinary shell 

 markings do not appear to be appreciably modifi.ed. After the 

 moulting of an ephippium, the back of the animal shows a little 

 crumpling, reminding us of what we find in such a marked degree 

 in the Daphnidae after the throwing off of an ephippium. 



Leydigio2?sis curvirostris Sars. 



This species has been hatched from dried mud from Sao Paulo, 



in Brazil, by Professor Sars, who kindly sent me some ephippial 



females for examination. There is no alteration in outline, but 



the valves are seen at once to be much darkened over nearly the 



