192 CRETACEOUS LAMELLIBRANCIIIA. 



Pkoten (^(iUirKOTEN) sAKiTMKNSis, sp. iiov. Plate XXXVII, figs. ], 2(1,1), :3. 



Description. — Shell small, slightly inequilateral, height and length nearly equal, 

 outline rounded, convexity small. Apical angle 107° to 111°. Ears rather large. 



Right valve ornamented with very numerous (fifty to sixty) narrow, well- 

 marked, radial ribs, which are separated by deep, narrow grooves. The ribs are 

 often slightly unequal, sometimes alternately, the smaller ribs being introduced 

 later than the larger. The ribs bear numerous small, similar, spiny scales, placed 

 either vertically or sloping, and sometimes having a roughly concentric arrangement ; 

 near the umbo concentric lamella occur. Postero-dorsal margin with fine oblique 

 striae. Anterior ear long, with a deep sinus and four radial ribs with spines. 

 Posterior ear much shorter, with three or four radial, spiny ribs. 



Left valve not seen. 



MeasuremenU : 













(1) 



(2) 



(3) 



(4) 



Length 



8-5 



7-0 



(3 



5*25 mm, 



Height 



8-0 



6-75 



G 



5-0 „ 



(1 — 4) A. quadratus zoue, East Harnham, Salisbury. 



Ajfjinities. — In form this species resembles P. campaniensis, but is easily 

 distinguished by the much larger number of ribs. The ornamentation resembles 

 that of P. pexatus, but the shell is without radial folds, the ribs are fewer, and the 

 apical angle larger. Radial folds occur on even the smallest specimens of 

 P. pexatus. 



Types. — In Dr. Blackmore's collection. 



Distrihution. — A. quadratus zone of East Harnham (Salisbury). /?. mncronafa 

 zone of Clarendon (Salisbury). 



Pkgten (^QUirECTEN) CAMrANiENSis, irOrbir/uy, 18 1<7. Plate XXXVII, figs. 4 — 8. 



1847. Pecten campaniensis, A. d'Orliuj/iy. Pal. Fran^. Terr. Crct., vol. iii, p. 



620, pi. ccccxl, figs. 12—16. 

 18.50. — — — Prodr. de Pal., vol. ii, p. 251. 



1870. — — F. J. Pidet and G. Campiche. Poss. Terr. Cret. Ste. 



Croix (Mater. Pal. Suisse, ser. 5), p. 215. 

 1887. — — A. Peron. Hist. Terr. Craie S.E. du Bassin Anglo- 



Parisien (Bull. Soc. Sci. hist, et nat. 

 de rYoniie, ser. 3, vol. xii), p. 163. 

 1889. — -^ 0. Gricpetikerl. Senon von Kiinigslutter (Palaeont. 



Abliaudl., vol. iv), p. 44, 



