Fossils from the Upper Mnsashino of Kazusa and Shimosa. 191 



and oval with the sharper end at the posterior ventral corner. 

 Antero- and postero-dorsal margins insensibly passing respectively 

 into anterior and posterior ends which are both rounded, with the 

 latter much more sharply than the former. Ventral margin broadly 

 arcuate, crenate within. Ligamental area comparatively narrow, 

 triangular, with two series of several straight grooves, the one 

 parallel to the anterior and the other parallel to the posterior side of 

 the area, which meet at an obtuse angle below the beak. Beaks 

 small. Surface with fine, straight, radiating, impressed Unes. 



A shell quite Kke this fossil was found living on the coast of 

 Awa (Boshu) with the posterior dorsal slope sometimes more 

 straight, so that the posterior end appears more angulate. The 

 surface is coloured brownish yellow with white radiating lines Hke 

 those of Pectunculus albolineatus and P. vcstihis. Although it is a 

 Httle more convex than our fossil, there is no doubt of its being 

 the same speceis. 



Fossil occurrence. — Sliito. 



Living. — Central Japan. 



Family Parallelodontidae. 



Genus PARALI.EL01>0X, Meek et Wortheii. 



320. Parallelodou obliquatus, Yokoyama. 



PamlModon obUqmtvs. Yokoyama, Foss Miiira Peuin., p. 170, pi. XVIII, figs. 9-11 



Only a single left valve. 



Fossil occurrence. — Shito. Lower Musashino of Miyata, 

 Yokosuka and Koshiba. 



Living. — Northern and Central Japan. 



Genus CUCÏJI.I.AKIA, Deshayes. 



»31. Cucullaria orientalis, Yokoyama. 



Pi. XVn. Figs. 8, 9. 



A few isolated right valves. 



Shell very small, rather thick, moderately convex, trans- 

 versely elongated, narrowed in front, gradually dilated behind, 

 strongly inequilateral, with posterior side four times as long as 



