6 Art. 7. — M. Yokoyama : 



any angle into the broadly arcuate ventral margin ; anterior dorsal 

 nearly straight, posterior somewhat excavated. Surface ornament- 

 ed with ten coarse, flatly rounded, radiating ribs separated by very 

 narrow valleys. Beak pointed. Lunula present, though not very 

 distinct, short. Hinge with an anterior lateral tooth. Height 

 5.4 milhm. Breadth 5 millim. Depth 1.5 millim. 



The specimen is worn, but very characteristic in form. It is 

 somewhat like Venericardia toneana Yok. (Foss. Up. Musashino, 

 p. 163, pi. XIII, figs. 6, 7.), but it is higher and more pointed, 

 with a less number of ribs. 



14. Myotlora fltietttosa, Gould. 

 Myodora ßuctitosa. Yokoyama, Foss. Up. Musashino, p. 170, pi. XIV, figs. 6, 7. 



A single right valve. 



15. Thracia pubescens, PULTENY. 

 (PI. I., Fig. 1.). 

 Thracia puhescens. Wood, Crag Mollusca, Bivalves III, p. 259, pi, XXVI, fig. 1. 



A specimen with both valves preserved, though the left valve 

 is much broken. It is 60 millim. long, 42 millim. high, and 

 about 25 millim. thick, and is almost exactly like that figured by 

 Wood in his Crag Mollusca above cited. Hanley and Forbes de- 

 scribes the ventral margin as somewhat retuse on the posterior side 

 (British Moll,, I. p. 226). But it is uniformly convex as in the 

 Crag specimen. The posterior end of ours is a little fractured. 



This species is still living in the British seas as well as in the 

 Mediterranean, but up to this time, it has never been found 

 livdng in the seas around Japan. 



16. Mytilus sp. 



A cast of a right valve looking somewhat like that of Mytilus 

 gray anus Dkr. living in our seas. 



17. A.n,omia lunula, Yokoyama. 

 Anomia lunula. Yokoyama, Foss. Up. Musashino. p. 177, pi. XLV, figs. 22, 23. 



