348 PKOF. T. R. JONES ON THE OSTEACODA 



Oypridea purbeckensis, H. Woodward, Catal. Brit, Foss. Crust. 

 1877, p. 89. 



Ci/pris ? purhecJcensis, Jones, Proceed. Geol. Assoc, vol. viii. 

 1883, pp. 57, 58. 



Lengtli f mm. figs. 3-5 ; 1 mm. figs. 4 & 6 ; 1| mm. fig. 1 ; 

 1^ mm. fig. 2. 



Valves subreniform, arched on the back ; nearly straight, or 

 somewhat incurved, on the ventral edge; rounded at the ends, 

 broadly and obliquely in front. Edge-view acute-oval. Surface 

 smooth. Contact-margins simple. Insides of front and hind 

 margins are sometimes more bevelled than in fig. 1. 



The size and shape are both rather variable (compare figs. 1-6, 

 PI. IX). An exceptionally broad (high) left valve, with a remarkable 

 sharp tubercle (local hypertrophy ?) on the postero-dorsal edges, is 

 shown by fig. 6. Figs. 3 and 5 are smaller i-eniform individuals. Age 

 and sex probably determined these differences of size and shape. 



A broken valve from the Post-tertiary freshwater beds at Copford, 

 Essex, is figured (hind end upwards) in my ' Monograph Entom. 

 Tert. Form.' 1856, pi. 1, fig. 5a, which closely approximates in 

 form to fig. 1 of PL IX. here. It is the variety tumida, B.C. andE., 

 of Candona Candida. Cypris virens (Jurine), known also as 

 C. tristriata, Baird, is a recent form of very similar make, and in 

 G. S. Brady's " Monogr. Rec. Brit. Ostrac," Trans. Linn. Soc. vol. 

 xxvi. pi. 23. figs. 23-26, it is figured witn the little gape seen also in 

 our fig. 4, PL IX. 



On the specimen in the Mus. Pract. GeoL, Xb^, probably one 

 of the early slabs seen by E. Forbes, there are the two somewhat 

 differing forms, namely, the reniform and the siihreniform: They 

 have all been weathered, and one side-surface has especially been 

 thus modified, so as to account for the flat margin in the figure 

 given by Lyell, and in one of those in Forbes's two letters. This 

 specimen is referred, by error I believe, to the Middle instead of to 

 the Lower Purbeck in the Museum of Practical Geology (see above, 

 p. 325 note). 



YI. Genus Candona, Baird, 1845. 



Valves like those of Oypris. Difficult to be distinguished from 

 that genus except by comparison with known recent forms, the 

 structure of the soft parts supplying the critical difierences. The 

 general aspect of the Purbeck specimens here selected under this 

 head reminds us of Candonce rather than of Cyprides. 



11. Candona bononiensts (corrected, see above, p. 311), Jones. 



(PL IX. figs. 7, 8.) 



CytJiere holoniensis, Jones, 1882, Bullet. Soc. Geol. France, ser. g 

 vol. viii. pp. 615, 616, 1883 ; Proceed. Geol. Assoc, vol. viii. p. 5g' 



Length 1^ mm. 



Valves suboblong, almost equally rounded at the ends, constricted 

 a little in front of the middle, the posterior moiety being higher and 



