CYTHERE. 29 



region, and becoming more or less concentric or confused anteriorly. Edge view 

 long-oval. 



From the Fluvio-marine beds of Headon llill, Isle of Wight. (F. E. Edwards' 

 Collection in the British Museum.) 



31. Cythere poltptyoha, Beuss. Var. 7tov. Plate I, fig. 5. 



Ctthebb polyptycha, Beuss. G-eol. Mag., 18S7, p. 451. 



Somewhat trigonal-obvate ; the antero-ventral angle and the opposite hinge 

 both well developed. Anterior border nearly semicircular ; the posterior some- 

 what contracted. Surface puckered with nearly parallel but irregular longitu- 

 dinal ridges, with intermediate rough but obscure reticulation. The central 

 region swollen into a round boss. Except that this specimen is less quadrate, 

 possesses a boss, and is less distinctly reticulate, it closely resembles Reuss' 

 original figure, Haidinger's ' Nat. Abth.,' vol. iii, 1854, p. 83, pi. x, fig. 22, from 

 the Tertiary of Bohemia. 



This Cythere belongs to a group of which G. pusilla, Bosquet, ' Entom. Tert.,' 

 p. 85, pi. iv, fig. 7, may be taken as a type ; possibly embracing the species 

 referred by G. S. Brady, 'Trans. Zool. Soc.,' vol. v, 1866, p. 376, pi. lix, 

 fig. 10, to Reuss' G. dathrata (which does not appear to us to be identical), and 

 also O.pnmila, Gr. S. B., op. cit., p. 378, pi. Ix, fig. 7. The latter, though near 

 to our specimen, has far more irregular ridges. 



One valve, from the " Norwich Crag " of Southwold. (British Museum.) 



32. Cythere plioata, Miinster. Plate I, fig. 18. 



Cttheee plicata, Miinsfer. Jones, Monogr. Tert. Eutom., 1857, pp. 32, 33, pi. iv, 



fig. 16; pi. V, figs. 8 a— d; pi. vi, fig. 17; Geol. 

 Mag., 1887, p. 450. 



We have a narrow and compressed carapace, contracted posteriorly, from the 

 Belosepia-bed, Bracklesham. (British Museum.) This species is noticed in the 

 ' Geol. Mag.,' 1874, p. 479, as having been found in the London Clay of 

 Copenhagen Fields, with two species of Chara. 



. The specimen of this common species here figured is a narrow right valve. 

 C. plicata is found abundantly in the Upper Eocene of Colwell Bay, and its variety 

 LATICOSTA is plentiful in the Middle Eocene of Barton and HighclifF. 



