PECTEN. 209 
1878. Nerruea mquicosrata, H. Bayle. Explic. de la Carte géol. de France, 
vol. iv, pt. 1 (Atlas), pl. exxii, fig. 4. 
1882. Janina meuicosrata, P. de Loriol. Gault de Cosne (Mém. Soe. Pal., 
Suisse, vol. ix), p. 102, pl. xi, 
figs. 6—8. 
1885. — —_ F. Nitling. Die Fauna d. baltisch. Cenoman. 
(Palwont. Abhandl., vol. ii), p. 21. 
1893. — (Vora) meauicostara, R. Michael. Zeitschr. d. deutsch. geol. 
Gesellsch., vol. xlv, p. 237. 
1894. Vora xqurcostata, A. Hennig. Om Ahussandst. (Geol. Foren. i Stockholm 
Forhandl., vol. xvi), p. 520 
1895. Janrra mquicostara, FH. Tiessen. Zeitschr. d. deutsch. geol. Gesellsch., 
vol. xlviul, p. 472. 
1901-2. Vora mauicostata, P. Choffat. Faune Crét. Portugal, vol. 1, ser. 4, p. 152, 
pl. ii, fig. 10. 
? Non 1847. Prcren mauicosratus, J. Miller. Petref. Aachen. Kreideformat., pt. 1, 
p. 33. 
Non 1850. — — J. de C. Sowerby. In F. Dizon's Geol. Sussex, 
p. 356, pl. xxvui, figs. 17, 18 
= seavcostatus). 
Description.—Shell ovate, equilateral ; ventral margin very convex and rounded ; 
antero- and postero-dorsal margins slightly concave. 
Right valve very convex, with a prominent imeurved umbo, and with from 
thirty-four to fourty-four rather small, rounded ribs of nearly equal size, except 
those near the anterior and posterior margins, which are smaller. The ribs are 
separated by rounded furrows of about the same width as the ribs. Both ribs and 
furrows are smooth, or nearly smooth. Near the antero- and _ postero-dorsal 
margins are narrow, smooth areas without ribs, the anterior area being slightly 
smaller than the posterior. Ears of moderate size, triangular, nearly equal, smooth, 
or with fine concentric ridges. 
Left valve flat or shehtly concave, with ribs similar to those of the right valve. 
Measurements : 
(1) (2) (3) 
Length ; 14. : 10S 9 mm. 
Height : 16 ; 12 : Laas 
(1, 3) Upper Greensand (zone of Pecten asper), Haldon. 
(2) ” ro 1 3 »  Worbarrow. 
Affinities.—This species is distinguished from P. (Veithea) quinquecostatus by 
the ribs being of equal size, and smooth or nearly smooth; also by the ventral 
margin of the shell being evenly rounded and by the areas being without ribs. 
D’Orbigny’s figure shows six more prominent ribs, but I have seen faint indications 
