OF THE PTJRBECK FORMATION. 349 



more convex than the front portion. Edge-view of carapace acute- 

 ovate. Left valve the largest. Contact-margiDS simple ; the nearly 

 straight dorsal edge has the front hinge indicated by a slight angle 

 and a faint impression behind it outside. 



12. Candona ansata, sp. no v. (PI. IX. figs. 9-12.) 



Length | mm. to J mm. 



Valves suboblong, obliquely rounded at each end, the slopes being 

 antero- and postero-dorsal. Back straight; ventral edge slightly 

 concave, with its edge turned in at the middle and swelling out at 

 the posterior third, so as to form a sti^ong projection, almost like 

 the short, blunt handle of a crock (but upside-down). The surface 

 is smooth ; but in some cases the inside of the valve is pitted (by 

 the decay of tubules ?), and the bevelled translucent insides of the 

 front and hind margins show radiating tubules (fig. 9). Lucid 

 spots are visible in figs. 9-12, somewhat resembling those in 

 Gytheridea. Edge-view of the carapace suboval. Left valve the 

 largest. The contact-margins are simple ; terminal edges bevelled 

 inside ; hinge-line distinct, with a faint angle in front (not strong 

 enough in fig. 9), and a slight impression behind it on the outside. 



The " lucid spots " are visible in a specimen from HartweU 

 (No. 269). 



They form a pattern of six ; four transverse, parallel^ in a curve 

 (convex backwards), and two in front, one near each end of the lower 

 row. 



VII. Genus Cytheee, Miiller, 1785. 



Carapace of two nearly equal valves, suboblong, subrhomboidal, 

 or subtriangular, thick, ornamented with pits, reticulation, riblets, 

 and tubercles. Left valve usually rather larger than the right. 

 Inside of the front edges in each valve bevelled off inwards. Hinge, 

 for the most part, a barlike ridge on the left valve, ending in front 

 with a tooth and a socket beyond, and ending behind at the socket 

 which receives the tooth at the end of the furrow on the right valve 

 behind the anterior tooth which falls into the front socket of the 

 left valve. So that, typically, the left valve has a bar and front 

 tooth, and a socket at each end; whilst the right valve has a 

 corresponding sulcus and socket and a tooth at each end, besides a 

 thin outer ledge or fiange to fall into a furrow along the outer 

 convexity of the wider left valve. Some of these features are often 

 modified or obsolete. See examples in the Monogr. Tert. Entom., 

 Pal. Soc. 1856. For the relationship of recent species, as based on 

 the soft parts, see the memoirs by Sars and Brady on Ostracoda — for 

 instance, G. S. Brady's " Report on the Ostracoda dredged by 

 H.M.S. ' ChaUenger,'" &c. 'ZooL ChaU. Exped.' pt. 3, 1880, 

 pp. 61-62. 



13. Cythere transiens, sp. nov. (PI. IX. figs. 13-16.) 



Length | mm. 



Valves subtriangular, or somewhat pear-shaped, rounded at ends, 



