340 Prof. T. R. Jones and Dr. H. B. HoU on the 



to advanced age ; but G. Renter, following R. Ricbter *, thinks 

 that the eggs may have lain within that lobe. A. Krause 

 adopted this view hypotheticallj in his memoir (Z, d. d. g. G. 

 vol. xxix. 1877, p. 32) . They support their view by referring 

 to Zenker's description f and figure of a right valve of a 

 female Cythere gihha, with a distinct lobular swelling at the 

 middle of the ventral border, rather bigger in its posterior than 

 in its anterior moiety ; its length is less than a third of that 

 of the valve, and its width (height) is about one third of that 

 of the valve. 



Cytherura gihha [Cytliere^ Miiller) is a well-known species, 

 studied by Lilljeborg, Zenker, G. 0. Sars, G. S. Brady, and 

 D. Robertson. As with most of the Ostracoda, the female of 

 C. gihha has a broader (that is, a more swollen) carapace than 

 the male. In the genus Cytherura tliis thickness or lateral 

 fullness is variable, and sometimes becomes strong and promi- 

 nent, as in C. Rohertsoni and C. gihha ; but it is not localized 

 as an isolated lump, as in Zenker's figure, which may 

 be an accidental exaggeration, due possibly to malfor- 

 mation of the individual J. Certainly the female fullness 

 of the carapace is strongest in the posterior moiety of the 

 valves, in accordance with the postero-dorsal position of 

 the ovaries in Ostracods and the Limnadiad Phyllopods, 

 but for \\hich a postero-ventral position would be quite 

 abnormal, as intimated in the Proc. Geol. Assoc, Pal. Biv. 

 Entom. p. 11. An analogue for the postero-ventral position 

 of the ovaries might possibly be found by referring to the 

 arrangement of the eggs in some Schizopods with their 

 '^ brood-plates " or lateral supplementary laminar egg-covers ; 

 but this would be going too far from the simply bivalved 

 Ostracods. 



In the bivalved carapaces of recent Ostracoda the most 

 compressed end is found to be the anterior, and in the 

 majority of known forms this end is also the lowest (nar- 

 rowest). This rule was adopted when it was necessary to 

 refer >.y name to the extremities of the Beyrichian valves and 

 i.thfie "special lobes. These relative proportions in height 

 l'.^7,2,lth) and thickness are observable in most of the Beyrichice 

 excepting — (1) those which have naturally a semicircular 

 ventral border, and (2) those in wliich the variable lobe 



* Zeitschr. d. d. geol. Ges. vol. xxi. 18G9, p. 774, 



t " The female Lrings forth living youug, and for their development 

 the hinder body is enlarged by the two swellings " (Wiegmann's Archiv, 

 20. Jahrg. vol i. 1864, p. 85, pi. v. D. fig. 2). 



X In some Lepeiditice the margin of the right valve is thickened at the 

 same place. 



