PLICATULA. 137 



Affinities.— This sijecies appears to be closely allied to P. imhricata, Koch and 

 Bunker,! 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. 

 Garteroniana, and may even prove to be only a worn example of that species. 



Bemarl-s. — The only undoubted specimens which I have seen are the three 

 rather imperfectly preserved examples on which the species was founded. 



Ti/pes. — In the Woodwardian Museum. 



Distrilmtion. — Lower Greensand of Upware. 



Plicatula gurgitis, Fidet and Boux, 1853. Plate XXV, figs. 13 rr, h, 14--21. 



1823. Plicatula pectinoides, J. de C. Sowerhy (uou Lamarn/c). Miu. Conch., 



vol. V, p. 5, pi. ccccix, fig. 1. 

 1847. — RADioLA, A. cVOrbujny. Pal. Fran?. Terr. Crct., vol. iii, p. 683 



(partim), pi. ccccl.xiii, figs. 6, 7 (now 1—5). 

 1850. _ — _ Prod, de Pal., vol. ii, p. 139 (partim). 



1853. — GURGITIS, F. J. Pidet and W. Roux. Moll. Foss. Gres verts de 



Geneve, p. 517, pi. xlvii, fig. 4. 



1854. — PECTiNOiDES, /. Morris. Cat. Brit. Foss., ed. 2, p. 180. 

 ? 1855. — RADIOLA, G. Cotteau. Moll. Foss. de I'Yonne, p. 118. 



1871. — GURGITIS, F. J. Pidet and G. Campiche. Foss. Terr. Cret. Ste. 



Croix (Mater. Pal. Suisse, ser. 5), p. 272. 

 1875. — PECTINOIDES, A. J. Jiikes-Browne. Quart. Journ. Geol. Soc, 



vol. xxxi, p. 297. 



Nou 1846. Plicatula pectinoides, A. E. Beuss. Die Vei-stein. d. bohm. Kreidef., 



pt. ii, p. 37, pi. xxxi, figs. 16, 17 

 ( = P. Barroisi, Peron). 

 — — — — /. de C. Sowerhy. Trans. Geol. Soc, ser. 2, vol. v, 



p. 328, pi. xxii, figs. 6,9 { = P. 

 peregriiia, d'Orbigny). 



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, l)ut generally very convex, somewhat flattened 

 near the umbones ; left valve concave, sometimes flat. Right valve ornamented 

 Avitli 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, pi. vi, fig. 3 ; G. Bohm, ' Zcitschr. der deutsch. geol. 

 Gesellsch.,' vol. xxix (1877), p. 236; A. Wollemann, "Die Biv. u. Gastrop. des deutsch. u. hoUiind. 

 Neoc." (' Abhandl. d. k. preussisch geol. Landesanst.,' n. F., part 31, 1900), p. 23. 



18 



