PECTEN. 205 
1893. Janira (VoLA) quinquecosrara, R. Michael. Zeitschr. d. deutsch. geol. 
Gesellsch., vol. xlv, p. 237. 
1895. —  Quinguecosrata, FH. Tiessen. Tbid., vol. xlvii, p. 471. 
1896. Voxa quinquecostara, A, Rutot. Bull. Soc. Belge de Géol., ete., vol. x, 
p- 30. 
1897. — —- U. Séhle. Geogn. Jahresh. (1896), p. 40. 
-- — — KR. Leonhard. Kreideformat. in Oberschles. (Pala- 
ontographica, vol. xliv), p. 46. 
— — — A. Hennig. Revis. af Lamellibr. i Nilsson’s ‘ Petrif. 
Suecana Form. Cret.’ (Kon. Fysiogr. 
Sallsk. i Lund. Handl., N. F., 
vol. viii), p. 52. 
? 1900. — _— G. Miller. Verstein. des Jura u. d. Kreide. 
(Deutsch-Ost-Afrika, vol. vii), p. 565, 
pl. xxiv, fig. 1. 
1901. — ~- H. Imkeller. Die Wreidebild. Stallauer Eck u. 
Enzenauer Kopf  (Palonto- 
graphica, vol. xlviii), p. 32. 
1901-2. — — P. Choffat. Faune Crét. Portugal, vol. i, ser. 4, 
p. 148, pl. iui, fig. 7. 
1902. — — J.P. J. Ravn. Mollusk. i Danmarks Kridtafl. I. 
Lamellibr. (D. Kel. Danske vid. 
Selsk. Skrift. 6 Rekke, nat. og 
math., vol. xi), p. 95. 
Non 1850. Prcren quinquecosratus, &. Kner. Verstein. Kreidemerg. von Lemberg 
(Haidinger’s Naturwiss. Abhandl., 
vol. 111), 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 mcurved 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. ‘he interspaces between the main ribs are flattened or 
sometimes slightly concave; in the larger number of cases four ribs occur in each 
interspace, but occasionally there are three, five, or six ribs in one or more of the 
interspaces—not infrequently the interspace next the posterior area has five 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 five to eight 
ribs. Both ribs and grooves are crossed by numerous fine, regular, concentric 
7 
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