Fossils from the Upper Musashino of Kazusa and SViimosa. 123' 



Fossil occurrence. — Otake, Sbisiii. Kamenari. Tega, Sbito. 

 Oji in Musashi. Lower Musashino of Miyata, Yokosuka, Koshiba. 

 and Naganuma. 



IS«. Corhula fretjuens, Yokoyama. 

 PI. VI. Fio-. 16, 17. 



Shell rather thick anil solid, triangular in outline, moderately 

 swollen, inequivalve. subequilateral, anterior side a little longer 

 than posterior, anterior margin broadly rounded, posterior obliquely 

 truncate (the obliquity being very variable; when it is very great, 

 the truncation becomes indistinct and the posterior end appears 

 more or less beaked), ventral margin arcuate. Surface with rough 

 lines of growth making it more or less concentrically unduhite. 

 A blunt keel runs from the beak to the postero-ventral corner of 

 the shell. Tooth of the right valve strong and triangular, that of 

 the left smaller and divided into two lobes by a groove rumiing 

 longitudinally. PaUial line distinct, with sinus very shallow. 

 Anterior muscular impression olongated, with the lower half 

 broader than the upper, posterior ovate. 



The following are some of the measurements: 



Length. Height. Depth. 



Eight valve (\erv obliquely truncate). 31.4 miUim. 23.2 millim. 9.4 millim 

 „ (less „ „ ). 22.8 „ 16.8 „ 6.5 „ 



„ „ (least „ „ ). 22.1 „ 16.3 „ 7.5 „ 



Left „ (tery obliquely „ ). 22.() „ 17.2 „ 6.7 „ 



Although the outline is rather variable, the proportion of 

 length to height is tolerably constant, being 10 to 7.3-7.6. 



Fossil occurrence.— Otake, Shisui, Tega, Shito (abundant). 



1ST. Corhula piinfulosa, Yok(^yama. 

 Pi. VI. Fig. 18. 



Shell moderately thick, transversely ovate, inequivalve, 

 nearly inequilateral, tlie beaks being only a little in front of the 

 middle; anterior margin more or less rounded, posterior obliquely 



