Fossils from the Miura Peninsula and its Immediate North. 1 55 



form and furnished with five coarse, broad, Sattisli, radial ribs 

 which are again divided into a few (generally four) unequal riblets. 

 The interspaces are somewhat, narrower than the ribs and arc also 

 furnished with several riblets which are finer than those on the 

 ribs. The cars arc broken, 



On comparing our specimen with the Living ones, it agrees 

 with the above named species in general, but with this difference 

 that the riblets on the ribs arc; larger than those of the interspaces 

 while in the living forms they arc nearly equal. 



Fossil occurrence: — Koshiba Zone (Kosh i ha). 



laving: — Northern Japan; Sea of Ochotsk; Alaska. 



L99. Pecten tigerrinus, Müller. 

 Pl. XIV. Figs. 5, 6. 



Pecten tigerrinus, Mülles, Zool. Dan. Prod., I, p. 248, No. 2993. Ntst, Desor. d. Coq. et 

 Polyp. Fossil. Tert. do Belg., p. 303, pl. XXIII, figs. 4 10. Conch, d. Terr. Tert. do la 

 Belgique, pt. I, p. 152, pl. XV, figs. 4. Yokoyama, Pectens from th<' Koshiba Neogene, Jour. 

 Gool. Soc. Tokyo, vol. XVIH, No. 208, p. 3, pl. I, figs. 11-12. 



Pecten tigrinus. Wood, Crag Mull., Bivalves, p. 27, pl. V, figs. 2. Lovkn, lad. Moll. 

 Scand., p. 31. Forbes and Hani.ky, Hist. Brit. Moll., vol. II, p. 285, pl. I. tigs. 8 11. Reeve, 

 Conch. Icon. pl. XXVIII, fig. 122. 



Pecten olsoletus. Sowkbby. Min. Conch., VI, p. 79, pl. DXLI, figs. 1-8. 



There are two valves, a left and a right, of which the former 

 measures 32 milliin. in height, .'50 millim. in length and about 

 8 millim. in depth, while the latter is much smaller, being 20 

 millim. in height, 18 millim. in length and about 4,5 millim. in 

 depth. Both arc; somewhat convex, roundly ovate in form, near- 

 ly equilateral and provided with numerous, very unequal, round- 

 ed, radial ribs of which about live are especially large. ( >f these 

 five, the one situated near the middle of the shell is the largest. 

 The inside of the shell are also radiately ribbed, the ribs and their 

 interspaces corresponding respectively to the interspace- and ribs 

 of the outer surface. The left valve is furnished with a broad 

 concentric constriction at about one-fourth the height from the 

 ventral margin. The inner margin is irregularly wavy. The ears 

 are unqual. 



Pecten tigerrinus is a very variable species, the shell being 



