]94 Art. 1. — M. Yokoyama : 



wliich were found in the latter liave neaily tlie same shape as the 

 right. As to the surface- sculpture, most of the specimens are 

 water-worn and smooth, but in one or two unequal concentric 

 striae are visible which are crossed b^ very fine, rather indistinct, 

 radiating lines. 



The largest of the left valves is 6.4 millim. long, 5.8 millim. 

 higli and 1.9 millim. deep. 



Fossil occurrence. — Shito. Lower Musashino of Miyata and 

 Koshiba. 



336. LiinÈOitsis ftreolata, Yokoyama. 

 PI. XVn. Figs. 6, 7. 



Shell small, thick, compressed,' obliquely short-oblong, inequi- 

 lateral, rounded both in front and behind, though somewhat more 

 sharply in the former than in the latter. Surface with fine im- 

 pressed radiating lines interrupted by unequal concentric grooves. 

 Beaks small and rounded. Hinge bent with teeth thick, lamellar 

 to tubercular, about six in anterior row, somewhat less in posterior, 

 rapidly diminishing in size in both roAvs from the middle to 

 both sides. Ligamental pit broadly triangular. A deep narrow 

 escutcheon is present just above and behind the posterior row 

 of teeth whereby the hinge-margin behind the teeth is somewhat 

 pushed inward. Beaks small, pointed. Fine radiating lines 

 present just within the palliai line. Inner margin flattened and 

 smooth. 



The measurements of four isolated valves are as follows: 



This shell is easily recognized by its shortty oblong shape 

 and the deep escutcheon behind the beak. 

 Fossil occurrence. — Shito (rare). 



