158 Art. 6.— M. Yokoyama: 



There are several specimens of this species, but the preserva- 

 tion is bad, though sufficient to show that they belong to a still 

 undescribed species. The largest right valve measures about 130 

 millim. in height. One of the right valves, comparatively well 

 preserved, is about 85 millim. high, 75 millim. long and 8-9 

 millim. in depth. 



Rather frequent at Zushi. 



Fossil occurrence. — Miyata Zone (Harashita in Shimo-Miya- 

 ta); Yokosuka Zone (Zushi), 



203. Pecten tokunagai, Yokotama. 

 Pl. XII. Fig. 1. 



Pecten tokunagai. Yokoyama, Pectens from the Koshiba Neogene, Jour. Geol. Soc. Tokyo, 

 vol. XXVIir, no. 208, p. 4. pl. I, fig. 2. 



Only a single valve (right?) partly broken, and about 68 

 millim. in height. It is thin, orbicular, moderately convex 

 (about 12 millim. deep) and furnished with about thirty-three 

 simple, flatly rounded, subequal, straight, radiating ribs which are 

 indistinct near the beak. The interspaces are much broader than 

 the ribs themselves, finely reticulate, and occasionally with a 

 secondary riblet which vanishes much more quickly than the main 

 ribs towards the beak. The ears are nearly equal and ornamented 

 with flat perpendicular riblets which together with the interspaces 

 are again perpendicularly striate. 



Fossil occurrence. — Koshiba Zone (Koshiba). 



204. Pecten tokyoensis, Tokunaga. 

 Pl. XIV. Figs. 7, 8. 



Pecten tokyoensis, Tokunaga, Foss. Env. Tokyo, p. 65, pl. V, figs. 1-10. 

 Pecten plica. Brauns, Geol. Env. Tokio, p. 48. 



A large inequivalved Pecten mistaken by Brauns for Pecten 

 plica L. was fully described by Tokunaga in the above cited work. 

 The right valve of this shell which is tolerably convex shows a few 

 broad flattened ribs often divided into several indistinct riblets 

 and separated by mostly shallow, and narrower interspaces. The 



