2 28 NEW YORK STATE MUSEUM 



York. These are large and strongly plicated shells. Professor Hall 

 subsequently abandoned this name in favor of Lunulicardium, which he 

 recognized as congeneric with his species. There can be no question that 

 they are in strict construction congeneric with Miinster's L. semi- 

 striatum; and it may be well to remark here that, in the material which 

 has been before us, every shade of transition in degree of plication is 

 present from those having it strongly marked, as in the species just cited, 

 to those in which the surface markings are the finest radial lines, and 

 further to forms in which the surface is without any trace whatever of 

 such lines. 



Chaenocardiola Holzapfel, 1889. In these shells there is a difference 

 from others in the great length of the truncating hiatus, the margins of 

 which in typical expressions extend nearly the full axial hight of the shell, 

 and cut the basal margin almost in the middle. The beaks are opisthogyre 

 or twisted backward. Were it not for the fact that every degree of varia- 

 tion is presented among these shells in the position and length of the 

 truncating margins, rendering it possible to construct series on the one 

 hand, truncating in a very short and sharply upturned anterior margin, 

 and, on the other, in a long straight, nearly axial, truncating margin, as in 

 typical forms, we should find some basis for recognition of this proposed 

 genus. Our material however does not justify us in separating the shells 

 except in extreme cases and in a subgeneric way, from Lunulicardium. 



Prochasma Beushausen, 1895. These are species of smooth or finely 

 lineate surface and generally with short hiatus. The beaks are regarded 

 by the author as prosogyre or turned toward the hiatus. Beushausen 

 specified as the type species Lun. pyriforme Miinster and embraced 

 within the group elongate mytiliform shells like Lun. mulleri Holz. as 

 well as broader and stouter species (P. bickense, P. d i 1 a t a t u rri ), 

 which have close allies among the New York shells. We have not been 

 able to substantiate Beushausen's observations on the direction of the beaks. 

 Shells of this type of structure, of which many (including specimens from 

 the Westphalian localities) have been closely studied by us, fail to convince 



