Fossils from the Miuta Peninsula ami its Immediate North. 17$ 



Family Nuculidse. 

 Genus Nucula, Lamarck. 



230. Nucula insignis, Gould. 

 Pl. XIX. Figs. 7, 8. 



Nucula ins'gnis. Gould, Otia Conch ologica, p. 175. Tokunaga, Foss. Env. Tokyo, p. 56. 



One right and ono left valve; the former 9 millim. and the 

 latter 8 millim. in length. These are to he identified with the 

 species above named occurring in great numbers in the Upper 

 Musashino of the neighbourhood of Tokyo, and which may be 

 described as follows: 



Shell small, rather solid, obliquely ovate-triangular, convex, 

 very inequilateral, posterior side very short and obliquely truncate- 

 at margin, with the postero-ventral junction subangulate, posterior 

 side very long, more than four times that of the anterior, sharply 

 rounded at end, ventral margin broadly arcuate. The sculpture con- 

 sists of numerous rounded riblets, broader than the interspaces 

 diverging from the median line of the shell to both sides; these riblets 

 often also bifurcate near the ventral margin, giving rise to several in- 

 verted v-shaped figures. Beaks small, but prominent. Area cordate, 

 bounded by obtuse ridges running from the beaks to the postero- 

 ventral corners, with the lips somewhat pouting and the surface 

 ornamented with diverging riblets like those of the other part of 

 the surface. Ligamental pit obliquely triangulär. Hinge bent, the 

 anterior teeth about twenty, occupying a little more than two- 

 thirds the length of the posterior hinge-line and generally curved 

 outward, the posterior teeth about ten, also generally curved out- 

 ward and often knee-shaped. Inner margin smooth. The largest 

 shell attains about 15 millim. in length, 12 millim. in height and. 

 8 millim. in thickness. 



Fossil occurrence. — Koshiba Zone (Koshiba); Upper Musashi- 

 no of Musashi, Shimosa and Kaz,usa. 



Living. — Northern Japan (north of 37° N. Lat.) 



