U2 CRETACEOUS LAMELLIBRANCHIA. 



1887. Plicatula Bareoisi, A. Peron. Hist, du Terr, de Craie (Bull. Soc. Sci. 



Hist. Nat. de I'Yonne, ser. 3, vol. xii), 

 p. 167, pi. ii, figs. 5—7. 

 1889. — soDOSA, A. Fritsch. Sfud. im Gebiete der bcihm. Kreideformat. 



IV. Die Teplitz. Schicht, p. 86, fig. 83. 

 1895. — ef. NODOSA, B. Liindgren. Mollusk. i i¥"aj?i?)a7/.-och Mticron- 



zouerna i nordostra Skane (K. Svenska Vet.- 

 Akad. Handl., n. s., vol. xxvi, No. 6), p. 41. 

 1897. — Bareoisi, H. Woods. Quart. Joui-n. Geol. Soc, vol. liii, p. 388, 



pi. xxvii, figs. 18, 19. 



Description. — Shell small, ovate, rounded, a little oblique. Eight valve inflated, 

 with the apical part truncated by the attached surface, which is often fairly large. 

 Left valve flattened or slightly concave, often with a subcircular opening near 

 the umbo. Both valves ornamented with more or less numerous, strong, nearly 

 smooth and rounded ribs, separated by deep and well-marked grooves; the ribs 

 may bifurcate near the margins of the valves, and new ribs may be intercalated. 

 Strongly marked growth-lines occur at intervals, and also concentric lamellse, the 

 latter being most distinct on the left valve. 



Measurements : 



(1) 



(2) 



(3) 



(-1) 



5-75 



5-5 



5-0 



4" 5 mm. 



6-0 



6-0 



5-75 



5-5 „ 



Length .... 

 Height .... 



(1 — 4) from the Chalk Eock, near Winchester. 



Remarks. — This species was described and figured by Reuss as P. pectin oides^ 

 Sowerby, but it differs greatly from Sowerby's species. D'Orbigny referred it to 

 P. nodosa, Dujardin ; ^ Geinitz and Fritsch followed the same course. Barrois, 

 although using the name P. nodosa, stated that Dujardin's figure was very 

 incomplete, and consequently his specimens could not be identified as belonging 

 definitely to that species. Pei^on subsequently pointed out that the species under 

 consideration differs considerably from P. nodosa, Dujardin ; the latter being about 

 four times larger, more elevated, and ornamented w^ith large, simple, widely 

 separated ribs. He therefore described and figured it as a new species — 

 P. Barroisi. 



Types. — Reuss's specimens came from the Planer-Kalk and Pyrope Sand of 

 Irziblitz, and from the Planer-Mergel of Weberschan. Peron's figured specimens 

 came from the Upper Turonian of Valmy. 



Distribution. — Zone of B. Cnvieri of the Devon coast. Zone of T. gracilis of 

 the Devon coast and Dover. Zone of H. planus of Dover, the Sussex coast, 

 Twyford (Winchester), etc. Chalk Rock of Winchester, etc. Zone of M. cor- 



1 'Mem. Soc. geol. de France,' vol. ii (1837), p. 228, pi. xv, fig. 14. 



