D. J. SCOURFIELD ON EPHIPPIA OF LYNCEID ENTOMOSTRACA. 233 



some of which he forwarded to me for examination. A sketch 

 of one of these is given in Fig. 24, and it will be seen that, in 

 contrast to the two pre\'ious species of Alonella, a considerable 

 amount of structural modification of the shell has taken place. 

 The dorsal outline has been slightly angulated as compared with 

 that of the parthenogenetic female [for a figure of the latter see 

 (5) PI. 5, Fig. 5], there is a very great amount of thickening of 

 the dorsal margin, and the shell markings have been very much 

 increased in intensity over the darkened area — so much so, in fact, 

 as to produce the appearance of a series of strong wavy longitudinal 

 lines in the dorsal region. The markings just over the egg itself 

 are hexagonal, and possibly this is the real structure everywhere, 

 but it is not very plain in other parts of the shell. The chitin 

 over the darkened area is minutely pitted. No line of weakness 

 could be discovered in these preserved specimens, and, owing to 

 the opacity of the shell, it was not possible to make out whether 

 the inner lining was undergoing modification or not. 



Alonella karua (King). 



Some ephippial females and moulted ephippia of this species, 

 from Itatiba in Brazil, have been received from Professor Sars. 

 The ephippium, with the ventral margins of the shell not wholly 

 separated, is shown in Fig. 25. It consists of a large part of the 

 shell, which is very considerably darkened, and thickened at the 

 back. The chitin of the shell over the darkened area is 

 minutely pitted, while the surface markings (longitudinal lines) 

 are obscured, although not quite obliterated. A line of weakness 

 is formed which runs out to meet the ventral shell margin just in 

 front of the little teeth at the posterior ventral angle. The most 

 striking feature about this ephippium, however, and one reminding 

 us in some respects of Alonopsis ambigua and Alona tenuicaudis, 

 is the excessive development of the inner membrane into a mass 

 of chitinous cellular " packing " over a sharply defined area. The 

 cellular character of this material is not-e very where apparent, and 

 true membranes exist in addition to the irregular spongy tissue. 



Peratcwantha truncata (O. F. Miiller). 



With this species we reach the first of a type of ephippium 

 which may be termed the Pleuroxus-Chydorus type, the main 

 feature of which is that the dorsal margin, instead of being nearly 



