Fossils from the Miura Peninsula and its Immediate North. X71 



ly striated tooth in the posterior portion and two such in the an- 

 terior, with a few (mostly about four) crenular teeth behind the 

 anterior horizontal ones which may be sometimes very inclistint 

 or obsolete; of the three posterior teeth, the middle one is the 

 longest and the lower one the shortest, Inner surface with radia- 

 ting lines. Proportion of length to height and thickness 100 : 53: 

 30. The largest specimen measures about 53 millim. in length. 

 Rather rare. 



This species has some resemblance to the one described by 

 Smith as Macrodon dalll (Challenger Lamellibranchiata, pi. XVII, 

 rig. 10) from off Kobe at 50 fathoms, although it is more oblique 

 and possesses a somewhat different dentition. 



Fossil occurrence. — Miyata Zone (Shimo-Miyata and Okine); 

 Yokosuka Zone (Otsu); Koshiba Zone (Koshiba). Upper Mu- 

 sashino of Kazusa. 



Living. — Northern and Central Japan (coasts of Sagami and 

 Hitachi). 



Family Limopsidae. 



Genus IAmopsis, Sassi. 



222. Limopsis auritoides, Yokoyama. 

 Pl. XVIII. Figs. 12, 13. 



One right and two loft valves. The form is somewhat varia- 

 ble, but decidedly oblique and rounded ovate with the shell thick 

 and solid. The surface is nearly smooth, only showing distant im- 

 pressed radiating lines crossed by more or less distinct incremental 

 ones. Beaks small but pointed, situated in the middle of the hinge- 

 face. Ears small. Teeth rather coarse, sixteen to twenty-one, 

 straight and vertical in the middle of the hinge-line, oblique and 

 curved outward toward the sides. Ligamental area broadly trian- 

 gular, the breadth of the base being more than twice the height, 

 shallow. Inner surface with fine and close radiating lines most 

 distinct near the mantle-line. Inner margin smooth and sharp. 



