PECTEN. 215 



1847. Janira Dutemplei, A. d'Orbigny. Pal. Fraiif. Ten - . Cret., vol. iii, p. 646, 



pi. ccccxlvii, figs. 8 — 11. 

 1850. — — Prodr. de Pal., vol. ii, p. 253. 



— Pecten .equicostatus, /. de C. Sowerby, in F. Dixon. Geol. Sussex, p. 356 



(p. 380, ed. 2), pi. xxviii, 

 figs. 1 7, 18. 

 1854. — sexcostatus, /. Morris. Cat. Brit. Foss., ed. 2, p. 177. 

 1870. Janira Dutemplei, F. J. Pictet and G. Campiche. Foss. Terr. Oct. Ste. 



Croix (Mater. Pal. Suisse, ser. 5), p. 253. 

 1877. — A. Peron. Bull. Soc. geol. France, ser. 3, vol. v, p. 507, 



pi. vii, figs. 4, 4 a. 

 1887. Vola (Janira) Dutemplei, Peron. L'Hist. Terr. Craie (Bull. Soc. Sci. 



hist, et nat. de l'Yonne, ser. 3, 

 vol. xii), p. 164. 

 1889. — Dutemplei, 0. Griepenkerl. Senon. von Konigslutter (Palaeont. 



Abhandl., vol. iv), p. 48. 

 1891. J. B'dhm. Die Kreidebild. des Fiirbergs u. Sulzbergs 



(Palseontographica, vol. xxxviii), p. 83, 

 pi. iii, fig. 33. 

 1896. ?, A. liutot. Bull. Soc. Beige de Geol., etc., vol. x, 



p. 31, fig. 14. 

 ? 1901-2. — cf. Dutemplei, P. Choffat. Faunc Cret. Portugal, vol. i, ser. 4, 



p. 149, pi. iii, figs. 8, 9. 



Description. — Form /3 (from tlie Upper Chalk, figs. 1 — 5). Shell ovately 

 triangular, considerably higher than long, nearly equilateral. Ventral margin 

 nearly semicircular, but with concave incisions of moderate depth between the 

 main ribs. Both valves show well-marked growth-ridges at fairly distinct intervals. 

 Hinge-line relatively short. 



Right valve very convex, with six main ribs. Umbo greatly incurved and pro- 

 jecting beyond the level of the left valve. Antero- and postero-dorsal areas 

 usually sloping inwards and concave. The six main ribs are usually prominent, 

 and are separated by broad, concave, more or less deep interspaces. In the inter- 

 spaces there are from four to seven ' well-marked rounded ribs separated by furroAvs 

 of about the same width ; the central ribs are usually rather stronger than those 

 at the sides (near the main ribs). The number of ribs in the interspaces varies 

 in different specimens, and usually also in different interspaces of the same speci- 

 men ; rarely four ribs are found in each interspace, less rarely five in each, but 

 frequently five in four of the interspaces and six or seven in the remaining inter- 

 space, or the numbers in different interspaces maybe four, five and six, or five, six 

 and seven. The antero-dorsal area of this valve (/. e. t lie space between the anterior 

 main rib and the anterior margin of the valve) bears from six to eight narrow ribs 

 separated by broader furrows; these ribs are smaller than those in the interspaces 



1 Occasionally three or four very much smaller ribs are also present. 



