226 D. J. SCOUllFIELD ON EPHIPPIA OF LYNCEID ENTOMOSTRACA. 



Daphnidan ap23earance, is not, I believe, homologous to the 

 definite prismatic cell structure — the " Schwimmgiirtel " of 

 Weismann — found in the more typical ephippia of the higher 

 family. 



Euryalona occidentalis Sars. 



Preserved specimens of the ephippial female of this interesting 

 form have been sent to me by Professor Sars, who raised this 

 species from dried mud collected at Ipiranga, in Brazil. The 

 shell in this case (Fig. 11) is very evidently modified, for at the 

 first glance it is seen that the back, instead of being evenly 

 curved as in the ordinary female (see " Fresh-water Entomostraca 

 of South America" (6), Plate 12, Fig. 1), is produced in the 

 middle into a blunt angle. The thickening of the chitin from 

 just above this angle to the posterior dorsal corner is also well 

 marked, and there is a small, but very evident, darkened area of 

 a deep brown colour near the centre of the valves, though nearer 

 the back than the ventral margin. When the animal is viewed 

 from the front these darkened areas are seen to project very 

 considerably, thus showing that they will form a special chamber 

 to contain the resting egg. No line of weakness could be 

 made out ; but this, as already stated, does not preclude the 

 possibility of its existence. Judging from the apparent extra 

 development of the inner layer of the carapace, I should think 

 that when the ephippium is thrown off the egg becomes sur- 

 rounded by very evident membranes. 



Alona affinis (Leydig). 



The ephippial female of this species, some examples of which 

 I have been able to examine through the kindness of Prof. 

 Sars, shows a very strongly marked thickening of the chitin at 

 the back, and a very considerable darkening of the dorsal and 

 central parts of the shell (see Fig. 12). The dorsal thickening 

 is rather peculiar, in that it comes to an end a long way before 

 the posterior dorsal angle is reached. Over the darkened area 

 the structure of the chitin is somewhat altered, being full of 

 little pits, and the coarse shell markings are also somewhat 

 indefinite, but the excessively fine longitudinal striae are still 

 present everywhere over the shell. With some care a chain of 

 specially developed cells, forming a line of weakness between the 

 ephippium and the ventral portions of the valves, and also 



