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separated ones ; for Ort/iis and Dalnia]iella typify the Family Orthidae 

 WooDW., while ScJtizopJioria is a genus belonging to the Subfamily Rhipido- 

 niellinae Schuchert of the Family Rliipidomellidae Schuchert. They are 

 said to differ from one another in interior peculiarities, although their external 

 characteristics are rather similar. 



There is not sufficient material a.t the present writer's disposal to allow 

 Jiim to examine either the shell structure or other internal characteristics. 

 Consequently he is not able to determine the phylletic position of the species ; 

 lie can therefore but follow the most recent and most reliable result of 

 OujKiXG in regarding the species as a Dahnajiclln. Dalnianclla striatnla 

 from China is described in the following manner. 



Shell biconvex, transversely oval in outline, rather small in size. The 

 two valves sometimes almost equally convex, but usually the dorsal is some- 

 what deeper than the other. Hinge-line very short, only a little longer than 

 1/3 of the greatest width of the shell ; cardinal angles rounded. The ventral 

 valve is most strongly vaulted at or in the neighbourhood of its umbonal re- 

 gion, but very smoothly slopes down anteriorly. 



The ventral area is quite high, triangular, with a delthyrium at the 

 middle. The beak is pointed, but only very slightly curves over the area. 

 The median sinual flattening is not very obvious in the smaller examples, but 

 the anterior margin of even such specimens is somewhat deflected upwards 

 and suggests the possible existence of a wide flat sinus when mature. In the 

 larger patterns it is very well developed. The dorsal valve has its maximum 

 depth at the center, and it slopes down very smoothly in four directions. The 

 anterior half, however, is, strictly speaking, somewhat flattened rather than 

 convex. The area is much lower than that of the opposite valve, and is 

 directed almost perpendicularly to the latter. The beak is acute but not 

 crooked over the area. The tops of both the beaks are equally high. The 

 anterior border is concave in correspondence with the convexity of the op- 

 posite valve. The surfaces of both the valves are equally ornamented Avith 

 very fine thread-like radial striae that increase in number either by implanta- 

 tion or dichotomy at various distances from the beak : they are rounded on 

 the top. The interspaces are narrower than the striae themselves. The 



