CYTHERIDEA PERFORATA. 29 



II. Cytheridea, Bosquet, 1852. 

 See Supplem. Monogr. Tert. Entom., 1889, p. 36. 



1. CiTHERiDBA PERFORATA (Bomer). Plate I, figs. 1 — 4. 



Cttheeina perfoeata, Bomer. Neues Jahrb. f. Mio., &c., 1838, p. 516, pi. vi, 



fig. 11. 

 CxTHERE HiLSEANA, Jones (nou Burner). Monogr. Entom. Cret., 1849, p. 10, pi. i, 



figs. 1 a—ff. 

 Ctthebidea Jonesiana, Bosquet. Mem. Cour. Acad. R. Sci. Belg., vol. xxiv, 



1852, p. 38, and Mem. Comm. Carte geol. 

 Neerl., vol. ii, 1854, p. 74, pi. viii, figs. 

 5 a — d. 

 — — Beuss. Deuksch. Akad. Wiss. Wieu, vol. vii, 1854, 



p. 141. 

 Baiedia peefoeata. Bosquet. Mem. Cour. Acad. Belg., vol. xxiv, 1852, p. 24, 



pi. i, figs. 8 a — d. 

 CxTHEEiBEA PEEFOEATA, Joues. Monogr. Tert. Entom., 1857, p. 44, pi. iv, figs. 



14 a — e. 



— — — Geol. Mag., 1870, pp. 74 and 76. 



— — Jones and Skerborn. Geol. Mag., 1887, p. 445 ; and 



Suppl. Monogr. Tert. Entom. 

 1889, p. 39, pi. i, fig. 14. 



Fig. 1. Large valve (left). Length 77; height '5 mm. 



Fig. 2. Small valve (right). ,, "695 ; ,, '415 mm. 



Fig. 3. Right valve. „ '83 ; „ -5 „ 



Fig. 4. Left valve. „ -916 ; „ -55 „ 



This subtriangular Cytheridea is sufficiently well known from published descrip- 

 tions and figures. Four of those in the Monograph of 1849 are reproduced as 

 reductions, PI. I, figs. 1 — 4. The tubercles in the former fig. 1 a, were illusory, 

 and the black area in fig. 1 e was merely caused by the black wax of the mounting 

 showing through the shell. 



Localities. — Chalk, Horstead ; Chalk-rock, Dunstable ; Chalk-marl, Didcot and 

 Dover; Detritus, Charing; Gault, Folkestone, Leacon Hill, and Godstone; Green- 

 sand, Cambridge and Blackdown. A similar form occurs in the Upper Oolite at 

 Ridgway, Dorset. 



Foreign. — Chalk, Balsberg, in Sweden. See also Reuss, ' Elbthelgeb.,' p. 149. 



III. PsEUDOCYTHERE, G. 0. Sars, 1865. 



" Shell thin, pellucid, compressed, rounded in front, produced behind; hinge- 

 joint simple " (G. S. Brady, ' Challenger Report,' 1880, p. 144). 



