48 CRETA.CEOUS ENTOMOSTRACA. 



this respect also it differs from Kafka's " Bairdia " depressa,^ from Koschtitz in 

 Bohemia. 



Locality. — Chalky Kent. 



5. Cytherblla Williamsoniana, Jones. Plate III, figs. 55 — 62. 



Cttheeina seebata (?), Williamson. Mem. Lit. Phil. Soc. Manch., vol. viii, 1847, 



p. 79, fig. 74. 

 — pedata(?), Qeinitz. Versteiu. Kieslingwalda, &c., 1843, p. 6, pi. v 



(Nachtrag), fig. 13. 

 Cytheeella "Williamsoniana, Jones. Monogr. Entom. Cret., 1849, p. 31, pi. vii, 



figs. 26 a — h (and fig. 26 i var.). 

 Cypeidina leiopttcha, Beuss. Haidinger's Naturw. Abhandl., vol. iv, pt. 1, 1851, 



p. 49, pi. vi, fig. 11. 

 Cytheeella Williamsoniana, Bosquet. Mem. Comm, geol. Neerlande, vol. ii, 



1854, p. 62, pi. V, figs. 2 a—d. 



— — Beuss. Elbthalgeb., &c,, pt. 2, 1874, p. 153, 



pi. xxviii, figs. 9, 10 a, b. 



— — ^ Marsson. Mittheil., &c., 1880, p. 31, pi. ii, figs. 



8 a — c. 



Length -6 ; height '35 ; thickness "25 mm. 



The carapaces are subject to much modification in their relative thickness, 

 and the valves as to their superficial ridges and furrows, which are sometimes 

 coarse and low, and in other cases sharply defined (var. stricta) ; and in some 

 more regular and less interrupted than in others. The surface also may be 

 smooth (ordinary), or roughened with small tubercles and granulations (var. 

 granulosa). 



Localities. — Chalk, Horstead, Colchester, and South-east England, and Keady 

 Hill (Derry) ; Chalk-rock, Dunstable; Chalk-marl, Dover; Detritus, Charing; 

 Gault, Folkestone, Leacon Hill, and Godstone ; Greensand, Ventnor. 



Foreign, — Chalk, Limburg, Saxony, Isle of Riigen. 



5*. Cytheeella Williamsoniana, Jones, var. stricta, nov. Plate III, fig. 71. 



Length '7 ; height "4 mm. 



Like the ordinary or typical form, but sometimes larger, and having the 

 longitudinal and marginal swellings of the surface narrowed and defined as 

 ridges. 



1 ' Kritisches Verzeichniss d. Ostracoden d. bohm. Kreidef.,' p. 2, pi. i, figs, la, b ; and in ' Die 

 Crustaceen der bohm. Kreidef.,' by A. Fritsch and J. Kafka, 1887, p. 14, fig. 26. 



