114 Art 6.— M. Yokoyama : 



belong to the posterior side, 14 millim. in height, and 3,5 millim. 

 in depth. 



Fossil occurrence. — Miyata zone (Nagai and Kami-Miyata); 

 Upper Musashino of Musashi and Shim osa. 



Living. — Northern Japan according to Tokunaga. 



139. Tellina vestalioides, Yokoyama. 

 Pl. VII, Fig. 25. 



Two left valves. 



Shell transversely oblong, compressed, thin, somewhat in- 

 equilateral, the posterior side shorter than the anterior, anterior 

 border rounded, going over gradually on one side into the 

 sloping dorsal margin and on the other into the broadly arcuate 

 ventral margin, posterior border obliquely truncate, making- 

 obtuse angles with the gradually sloping dorsal margin as well as 

 with the ascending ventral margin, the angle with the former 

 being more obtuse than that formed with the latter. Surface 

 uniformly and flatly convex, except the region bounded by a very 

 obtuse umbonal edge and postero-dorsal margin which is some- 

 what depressed along the median line. The sculpture consists of 

 concentric incremental lines and very faint and unequal radiating 

 lines which are also seen on the inner surface. Cardinal teeth 

 two, the anterior in the left valve being bifid. Laterals indistinct 

 in the same valve. Posterior fold very slight. Palliai sinus 

 very deep, reaching almost to the anterior muscular impression. 

 Length 32 millim. of which 17,5 millim. belong to the anterior 

 side, height 19,5 millim., depth 4 millim. 



I'h is species is very closely related to Tellina vestalis Haxljoy 

 (Syst. Conch. Cab. Mart. Chemn., vol. X, pt. 4, Tellinidae, p. 

 174, pl. 35, figs. 9-11) from the Philippines, so closely, indeed, 

 that there is almost no marked difference in shape. But the 

 latter seems to differ from ours in the following points : very thin 

 and translucent shell, a single tooth in the left valve instead of 

 two, and absence of faint radiating lines. 



Fossil occurrence. — Naganuma Zone (Naganuma). 



Living. — Northern Japan (Hakodate). 



