Fossils from the Miura Peninsula and Its [mmediate North. J 4;-i 



lanceolate, distinct. Inner margin finely crenulate. The largest 

 specimen measures 16millim. (10) in length, 12 millim: (8,3) in 

 height and 9 millim (5,6) in thickness. Another specimen meas- 

 ures 15 millim. (10) in length, 12.5 millim. (7.5) in height and 10 

 millim. (6. 6) in thickness. 



This species closely resembles Crassatella sublamellata Kobelf 

 (Syst. Conch, Cab., XII, pi. 1, Crassatella, p. 25, pi. 7, fig. 11) 

 living in our seas which is, however, flatter and transversely more 

 elongated, with a less number of ribs. Crassatella simplex Kobelt 

 (loc. cit. pi. 7, fig. 10). whose habitat is unknown also resembles 

 our fossil, though the inner margin is smooth. 



Fossil occurrence. — Miyata Zone (Yamagayado in Kami- 

 Miyata), rare; Koshiba Zone (Koshiba), very frequent. Upper 

 Musashino of Kazusa. 



Family Myochamidae. 



Genus Myodora, Gray. 



180. Myodora reeviana, Smith. 



Pl. XI. Figs. 12, 13. 



MijOdora reeiiina. Pilsbry, New Jap. Mar. Moll., Peleeypoda, Proc, Acad. Nat. Sei. 

 Phi lad. July, 1904, p. 558, pl. XLI, figs. 7, 8, 9, 10. 



This species has been well described by Pilsbry in the above 

 cited work. The shell is roughly pentagonal, with the right valve 

 convex, and the left one flat and smaller. 



We possess one right valve and one left valve. The former 

 is from Koshiba and is 11,5 millim. long, millim. high and 8 

 millim. deep. It has about seventeen regular concentric grooves 

 on the surface. The latter is from Motowada, 6 millim. long and 

 5 millim. high, and its surface is more irregularly and shallowly 

 grooved. 



Myodora fluctuosa Gould which is so frequent in the Upper 

 jlusashino of Tokyo is distinguished from Myodora reeviana by 

 having a more excavated antero-dorsai margin and only roughly 

 undulated surface. 



