PLICATULA. 137 
Affinities.—This species appears to be closely allied to P. imbricata, Koch and 
Dunker,! from the Hilsthon of the Elligser Brink, but is distinguished by the left 
valve being flat or concave. The shell is also very similar in form to P. 
Carteroniana, and may even prove to be only a worn example of that species. 
Remarks.—The only undoubted specimens which I have seen are the three 
rather imperfectly preserved examples on which the species was founded. 
Types.—In the Woodwardian Museum. 
Distribution—Lower Greensand of Upware. 
PricaTuLa Gureitis, Pictet and Roux, 1853. Plate XXV, figs. 13a, b, 14—21. 
1823. Pricaruna pectinorpes, J. de C. Sowerby (non Lamarck). Min. Conch., 
vol. v, p. 5, pl. ecccix, fig. 1. 
1847. — rapioua, A. d’Orbigny. Pal. France. Terr. Crét., vol. iii, p. 683 
(partim), pl. eccelxiii, figs. 6, 7 (non 1—5). 
1850. — — = Prod. de Pal., vol. ii, p. 139 (partim). 
1853. — curaitis, F. J. Pictet and W. Roux. Moll. Foss. Grés verts de 
Gentve, p. 517, pl. xlvii, fig. 4. 
1854. — PECTINOIDES, J. Morris. Cat. Brit. Foss., ed. 2, p. 180. 
? 1855. — RADIOLA, G. Cotteau. Moll. Foss. de l’Yonne, p. 118. 
1871. — auraitis, F’. J. Pictet and G. Campiche. Foss. Terr. Crét. Ste. 
Croix (Matér. Pal. Suisse, ser. 5), p. 272. 
1875. — pectinorpEs, A. J. Jukes-Browne. Quart. Journ. Geol. Soc., 
vol. xxxi, p. 297. 
Non 1846. Puicatruta PEctinoiIpEs, A. EL. Reuss. Die Verstein. d. bdhm. Kreidef., 
pt. ii, p. 37, pl. xxxi, figs. 16, 17 
(= P. Barroisi, Peron). 
—_- — — — J. de C. Sowerby. Trans. Geol. Soc., ser. 2, vol. v, 
p. 328, pl. xxii, figs. 6, 9 ( = P. 
peregrina, VOrbigny). 
Description—Shell oval, more or less triangular, umbonal part generally 
produced; margins rounded, the postero-dorsal being often concave. Inequivalve : 
right valve sometimes only slightly, but generally very convex, somewhat flattened 
near the umbones; left valve concave, sometimes flat. Right valve ornamented 
with numerous narrow, sharp, radial ribs, curving and slightly irregular, separated 
by broad spaces. The ribs bear many spines, having usually a roughly concentric 
arrangement, and being longest near the margins of the valves. Concentric 
' «Norddeutsch. Oolithgeb.’ (1837), p. 50, pl. vi, fig. 3; G. Bohm, ‘ Zeitschr. der deutsch. geol. 
Gesellsch.,’ vol. xxix (1877), p. 236; A. Wollemann, ‘‘ Die Biv. u. Gastrop. des deutsch. u. holliind. 
Neoce.”’ (‘Abhandl. d. k. preussisch geol. Landesanst.,’ n. F., part 31, 1900), p. 28. 
18 
