Fossils from the Upper Musashino of Kazusa and Shimosa. 15T 



are indeed somewhat alike, but a closer examination shows that 

 Cardium californiense is flatter and longei'. 



Fossil occurrence. — ()take (numerous), Shito, Shisui, Tega. 

 Oji (ver}^ frequent). 



Family Leptonidse. 



Genus ^ONTACUTA, Turton. 



24S. Moufactita Jnponicft, Yokoyama. 



PI. IX. Figs. 2, 3. 



Shell very small, rather thin, moderately inflated, transversely 

 oval, very inequilateral with anterior side only about half as long 

 as posterior. Anterior dorsal margin steepty sloping, slightly ex- 

 cavated, meeting nearly at a right angle with posterior dorsal which 

 is less steej^ and somewhat convex. Anterior and posterior ends 

 rounded, the former a little more sharply than the latter. Surface 

 only with lines of growth. Beaks small, pointed. Muscular and 

 palliai impressions distinct. Length 3.5 millim. Height 3. 1 millim. 

 Depth of each valve about 1.1 millim. 



This species closel}^ resembles 3ïontacuta bklentata Mont. 

 (Wood, Crag Moll., Biv., p. 126, pi. XII, fig. 17) of the English 

 Crag, which is still living in the British seas. The English 

 species, however, is larger and more rhombic in outline, with the 

 dorsal and ventral margins subparallel. 



Fossil occurrence. — Otake, Shisui, Shito. Oji (numerous). 



Living. — Central Japan. 



249. Montacufa ohlongata, Yokoyama. 

 PI. Xin Figs. 9, 10. 



Shell very small, thin, compressed, transversely oblong, 

 very inequilateral, rounded at both ends, a little more sharply in 

 front than behind. Dorsal and ventral margins subparallel. 

 Surface smooth. Beaks small and pointed, with an obtuse keel 

 running to postero-ventral corner. Left valve with two diverging 

 teeth which are very distinct. Length 4.5 milhm. Height 3.1 

 millim. Depth of each valve about 1.0 millim. Very rare. 



