PECTEN. 205 



1893. Janira (Vola) cjuinquecostata, II. Michael. Zeitschr. d. deutsch. geol. 



Gesellsch., vol. xlv, p. 237. 



1895. — (iuiNQUECosTATA, E. Tiessen. Ibid., vol. xlvii, p. 471. 



1896. Vola quinquecostata, A. Eutot. Bull. Sou. Beige de Gl'oL, etc., vol. x, 



p. 30. 



1897. — U. Sbhle. Geogn. Jahresh. (1890), p. 40. 



R. Leunhard. Kreideformat. in Oberschles. (Palac- 



ontographica, vol. xliv), p. 46. 



A. Hennuj. Eevis. af Lamellibr. i Nilsson's 'Petrif. 



Suecana Form. Cret.' (Kon. Fysiogr. 



Sifflsk. i Lund. Handl., N. F., 



vol. viii), p. 52. 



? 1900. — G. Midler. Verstein. des Jura u. d. Kreide. 



(Deutsch-Ost-Afrika, vol. vii), p. 565, 

 pi. xxiv, fig. 1. 



1901. II. Imlceller. Die Kreidebild. Stallauer Eck u. 



Enzenauer Kopf (Palaeonto- 

 grapbica, vol. xlviii), p. 32. 

 1901-2. — P. Choffat. Fauue Out. Portugal, vol. i, ser. 4, 



p. 148, pi. iii, fig. 7. 



1902. J. P. J. Ravn. Mollusk. i Danniarks Kridtafl. I. 



Lamellibr. (D. Kgl. Danske vid. 

 Selsk. Skrift. 6 Esekke, nat. og 

 math., vol. xi), p. 95. 



Non 1850. Pecten quinquecostatu.s, B. Ener. Verstein. Kreidemerg. von Lemberg 



(Haidinger's Naturwiss. Abbundl., 

 vol. iii), p. 29 (? = striatocostatus). 



Description. — Shell ovate or somewhat triangular, nearly equilateral; height 

 sometimes equal or nearly equal to, but usually rather greater than, the length. 



Right valve moderately convex, with incurved umbo, and strong, rounded, 

 regular ribs. Six main ribs are rather larger than the others, and project at the 

 margin of the valve, forming angles between which the parts of the margin 

 are slightly concave ; the anterior and posterior main ribs are not quite so 

 strong as the others. The interspaces between the main ribs are flattened or 

 sometimes slightly concave; in the larger number of eases four ribs occur in each 

 interspace, but occasionally there arc three, live, or six ribs in one or more of the 

 interspaces — not infrequently the interspace next the posterior area has live ribs. 

 The two middle ribs of the interspaces are commonly rather stronger than one or 

 both of the laterals; sometimes one lateral is very small. The grooves between 

 the ribs are usually narrower than the ribs. Posterior area slightly larger than 

 the anterior; both with ribs which are smaller than those on the rest of the shell ; 

 the anterior usually with from four to eight, the posterior with from live to eight 

 ribs. Both ribs and grooves are crossed by numerous line, regular, concentric 



