436 CRETACEOIJS PELECYPODA 



AMUSIUM, Klein, 1753, (see p. 426). 

 1. Amusium ? MEMBRANACEUM, Nllsson, PI. XXXII, Pig. 5, and PI. XLI, Figs. 7-8. 



1827. Perten mcmbraiiaceiis, Nilss., Petrif. Suec, p. 23, pi. ix, fig. 16. 

 18(56. Idem, Zittel, Denksch. Akad., Wion, xxxv, pt. ii, p. 107, cum. syn. 



Am. testa ovato-orbiculari, cequivalvi, valde complanata, si(b-(Bq7iilaterali, temiis- 

 simci, Icevlgata aut concentrice subtiliter striata, nit Ida ; auriculis fere cequoUbus, 

 postica oblique dcsinente, antica subtrimcata. 



The Indian specimens do not exhibit any difference from the Eiiropean ones. 

 The superficial glassy layer is, as a rule, quite smooth, but when it has been removed 

 by decomposition, the shell exhibits a number of very fine radiately arcuate lines. 

 The gape of the valves must be very slight, if indeed it is at all marked, but the 

 structure of the shell appears to be that of Amusium. 



Localities. — Arrialoor and Karapaudy, in grey sandstone ; rare. 



Formation . — Arrialoor group. 



In Europe this species belongs to one of the commonest shells in the upper 

 and middle (Turonien) cretaceous beds ; it has been recorded from Sweden, Hanover, 

 at Maastricht, from near Aachen, in Saxony, Bohemia, at Lemberg (in Galicia), in 

 the Alpine Gosau deposits of Lower Austria, in Bavaria, &c. 



2. Amusium illustre, Stoliczka, PI. XLI, Pigs. 9. 



Am. testa onagiia, sub-orbictilari, valvis convex iiiscul is, crassis, ad umbones late 

 obtusatis, Icevibus, striis incrementi iiKequalibus, jiartim sub-obsoletis tectis ; auri- 

 culis sub-ceqiialibns, tnagnis, oblique trmicatis. 



One of the largest known cretaceous species of the genus, distinguished by 

 a strong, solid, almost smooth shell, obtuse umbones, and considerable convexity of 

 the valves; the ears are large and apparently very nearly equal. The valves appear 

 to have been slightly gaping at both ends. 



Locality. — West of Arrialoor, in light grey sandstone. 



Formation. — Arrialoor group. 



8. Amusium sulcatellum, Stoliczka, PI. XXXI, Pigs. 12 and 17. 



18-16. Pecten orhiciihiris, Sow.? apud Forbes, Trans., Geol. Soc, Lond., vii, p. 151, non idem Sow. 



Am. testa sub-orbiculata, valvis crassiusculis, (equilateralibns, parum convexis, 

 ad latera deplanati^, concentrice snlcis angustis ant lineis imjircssis subdistaufibits, 

 coiiceiitricis, coiifertis, notata, ceqiddistantibiis, lateraliter minus distinctis, interstitiis 

 planatis, snlcis mulfo latioribus, concentrice minutissime siriolatis ; aiiricnlis sub- 

 ceqnalibus, postica paulo minore, oblique et sub-Jlexiiose terminante, antica majore, 

 rectius trimcata. 



A sub-compressed, nearly orbiculate species of the type of A. orbiculare. Sow., 

 but with somewhat more acute umbones and much thicker shell. The ornament- 



