J- NEW YOKK STATIC MISKIM 



width of the valve in the middle part; cardinal extremities 

 obtusely anj^ular, having the appearance of flattened ears. 

 I'edicle valve uniformly and strongly convex; umbo slightly 

 projecting and very narrow, beak obscure. Cardinal area narrow 

 (?); interior of pedicle valve not observed. Brachial valve 

 strongly concave, beak hardly projecting beyond the long, 

 etraight hinge line. Cardinal extremities strongly developed, flat; 

 area very small; cardinal process small, bipartite on its anterior 

 face; the lobes being denticulaite anteriorly with from three to 

 five small denticles on each side. Crui-al plates very long 

 and slightly divergent; the lower portion produced on each side 

 as a strongly elevated w^all with perpendicular sides extending in 

 the original direction of the crural plates close to the ante-lateral 

 angle, where it recurves and returns, parallel to the median axis 

 and nearly in a straight line as a still more prominent wall merg- 

 ing into the base of the cardinal process. The elongate, sym- 

 metric, subrectangular spaces thus formed are each divided 

 transversely by a vertical ridge about one third of the length of 

 the valve from the cardinal line. The long narrow space between 

 the inner muscular walls is also bounded anteriorly by a low, 

 rounded, curving ridge and divided in the median line of the 

 shell by a low% rounded, longitudinal ridge. The anterior half 

 of the surface of the long anterior adductors is very rugose and 

 radially striated. 



The surface is covered with concentric lines of growth and 

 radiating, quite widely separated, filiform striae with smooth, 

 flat interspaces. 



Dimensions. Lenglh 0.7 mm. width 8.9 mm, hight 3.1 mm. 



Horizon and locality. Kysedori)h hill. The few specimens 

 obtained, among them a finely weathered interior of a brachial 

 valve, were found in the pebbles of black compact limestone, 

 together with IMectambonites sericeus, PJectam- 

 b o n i t e s p i s u m and O r t h i s t r i c e n a r i a . (Group 5) 



Observations. The genus Christiania was proposed by Hall and 

 Clarke for such species, formerly included in I^ptaena, as differ 



