30 / [Assembly 



The accompanying figures illustrate the principal characters shown in the 

 typical species R. formosa. 



.<^K^ 4^' S. >^ 





Fig. 1. Dorsal view of a specimen, natural size. 



Fig. 2. Interior of the dorsal valve enlarged two diameters, to show the broad cardinal 



process j which covers the extremitj^ of the beak, the bases of the crura c, 



and the short medio-longitudinal septum s. 

 Fig. 3. Profile view of the same, showing the cardinal and crural processes. 

 Fig. 4. Interior of the ventral valve, natural size, showing the teeth, the deltidium, 



and the foramen. 



Fig. 6. 



Fig. 5. The upper part of the two valves connected in their natural relations to each 

 other, showing the teeth, the ventral valve below, the sockets, base of crura, 

 cardinal process, and septum of the dorsal valve. 

 Longitudinal section, showing the foramen, the deltidium and the cardinal 

 process of the opposite valve lying beneath it; the crura, first bending down- 

 wards, and then recurved into the dorsal valve and its continuation in the 

 spire, with the descending process e, which forms, with the opposite one, a 

 connecting filament between the two spire*. 



The following species, published in the Report of the Regents of the 

 University for 1856, may be referred to this genus. 



Waldheimia glohosa 

 W. formosa 



W. deweyi 



W. 



rectirosti-a = 



Rhynchospira globosa ; 

 R. formosa ; 



R. deweyi ; 



R. rectirostra. 



See also the same species described in the Palasontology of New- York, 

 Vol. iii, pages 215, 216 & 217, Plates xxxvi & xxxvi a. 



Geological range. The species at present referred to this genus are from 

 the Niagara and Lower Helderberg groups'; while I have a single analo- 

 gous form, not yet fully determined, from the Hamilton group. 



