][32 •^'^ï- 1- — ^I- Yokoyama : 



times rather subtruiicate behind. Anterior and posterior margins 

 more or less straight, going over into lateral margins withont any 

 angulation; ventral margin arcuate, slightly gaping behind. Surface 

 more or less concentrically corrugated, especially so toward lateral 

 margins, somewhat flattened or even excavated a little behind the 

 middle. Palliai line and sinus generally indistinct, the latter large 

 but shallow and rounded. 



The largest right valve measures 18. 2millim. in length, 13 

 millim. in height, 4.1 millim. in depth, while the largest left 

 measures 14.6 millim. in length, 10 millim. in height and 3> 

 millim. in depth. 



This shell seems to have been more or less hyaline wheix 

 fresh, as some of the specimens show such a character and are 

 translucent. 



Fossil occurrence. — Tega (very frequent), Kamenari, Kioroshi. 

 202. Raeta iàtaf/nifiea, Yokoyama. 



PI. VIII. Fig-. 12, 13. 



Shell comparatively large, tliin, inquilateral, anterior side 

 somewhat shorter than posterior, transversely oval, swollen and 

 broadly rounded in front, compressed and quickly narrowed 

 behind, with the end truncate and a little gaping. Surface with 

 numerous irregular concentric plications. Main teeth rather 

 small, two in the left valve and one in the right, the posterior one 

 in the former being somewhat deltoid in shape. Posterior lateral 

 tooth very long. Palliai sinus very large and deep, horizontal, 

 finger-like. 



A single shell with both valves perfect. Length 42.5 millim. 

 of which about 20 millim. belong to the anterior side. Height 37 

 millim. Thickness 25.5 millim. 



This species is somewhat like Raeta anatinoides (Reeve) shown 

 in Conch. Icon., Mactra, pi. XXI, fig; 123 from an unknown, 

 locality, which, however, is more pointed behind. 



Fossil occurrence. — Tega (Kizaki). 



