6i 



The present writer does not, however, agree with Martelli in placing 

 it in the genus Schizophoria. In the genus OrtJiis " la rarita di forme h"scie, 

 prive di ornamentazione radiale," as Pellizzali observes, is rcall)- the case. 

 Or rather, no smooth form can be regarded as an Ortliis. Thus it seems 

 most reasonable to regard the fossil as a Trifilccin, as was done b>- Weli.er 

 in his report above mentioned. Of course a Triplccia may possess fine radial 

 striae : for Hali. says, " Surface with obscure concentric growth-lines, and fine 

 radiating strije on the inner laminjE ; in rare instances there are radiating lines 

 on the exterior.^' " Yet it is certain that the fossil is neither an Ortliis nor a 

 ScJiizophoria . 



Then Triplccia pol oi ixom Hu-pei ma)' be described somcwliat in the fol- 

 lowing manner. 



The shell is composed of two valves of unequal convexit)', and is re- 

 markably wider than long. In the anterior portion it is somewhat trilobate, 

 the mesial fold being very conspicuous there. The hinge-line is quite straight, 

 but rather short, being about one half of the greatest width of the shell in the 

 majority of the specimens. It is, however, by no means constant, and in some 

 of the examples it occupies about 2/3 of the ma.ximum breadth of the shell. 

 The ventral valve is shallow, convex about the beak, but very strongly 

 depressed by the development of a wide and deep mesial sinus in the 

 anterior margin. The width of the sinus along the front margin is about 

 1/3 of the entire antero-lateral margin of the shell. The area is low but 

 very distinctl}' realized, with a delthyrium in the middle, which is covered by" 

 a slighly convex deltidial plate probably with a foramen. The beak is some- 

 what attenuated and slightly overhangs the cardinal area. The dorsal valve is 

 by far the more convex and especially the median part of the visceral portion 

 is almost hemispherically gibbous, the gibbosity extending to the anterior 

 margin, so as to correspond to the sinus on the opposite valve. The beak is 

 less pointed than in the ventral valve and is less overhanging too. The area 

 also is consequently lower. Interiorly there are dental lamellfe or plates that 

 are rather short and somewhat diverging. On the surface of both the valves 

 hardly any trace of radial striie is visible, although a number of concentric 

 growth lines are developed, except in the marginal portion of the shell. 



I) Hall:— Nat. Hist. Kew York. Palaeontology, vol. VHI., pt. I., p. 270, 1892. 



