PLATE LXXV. 



(Tigures 1-6 by G. B. Simpson; 7. 9 by F. B. Heek; 9 by E. Emmons.) 



Genus RENSSEL^RIA, Hall. 



Pace 26S. 



RBNSSELiGRIA CaTUOA, Sp. IIOV. 



FIcB. 1, 2. Dorsal and ventral views of a specimen which retains most of the shell ; showing the fine sur- 

 face plication and the lenticular form of the valves. 

 Oriskany sandstone. Cayuga, Ontario, 



Ren88el.«;ria ovulum, sp. nov. 



¥\g. 3. An internal cast of the brachial valve ; showing the muscular scars, the large cavity left by the 

 hinge-plate, and the genital markings in the umbonal region. 



Fig. 4. An internal cast of the pedicle-valve ; showing the filling of the deep muscular cavity and its 

 division by the diductor and adductor scars, and the cavities left by the teeth. This species 

 differs from the foregoing in is persistently greater size, much more convex valves, and 

 coarser plication of the surface. It is a more orbicular and moi-e i-egularly convex shell than 

 R. ovoides. 



Oriskany sandstone. Cayuga, Ontario. 



RENL8EL.ffiRIA OVOIDES, EatOll. 



Tig. 6. An internal cast of the brachial valve ; showing the cavity of the hinge-plate, the branching 

 vascular sinuses in the umbonal region and the anterior and po.sterior division.^ of the adductor 

 muscular impression, the surface of the posterior scars being strongly marked with ramifying 

 lines. The structure and arrangement of all of these parts is strikingly similar to that occur- 

 ring in Amphigenia (see plate Ixxiv, fig 5). 



Oriskany sandstone. Sclwharie, New York. 

 Pig. 6. An internal cast of a pedicle-valve having a regularly oval outline, and showing the filling of the 

 muscular impression and the cavities left by the teeth. 



Oriskany sandstone, ^irnngport, Cayuga couvty. New York. 

 Fig. 7. The exterior of a pedicle-valve, having the characteristic inflexion of the lateral margins ante- 

 riorly, anil showing the fine surface plication. 

 Fig. 8. Profile of conjoined valves ; showing the usual convexity of the species. The shell of the 

 brachial valve has been exfoliated, losing its surface plicjition. 

 Oriskany sandstone. The Helderhergs, New York. 

 Pig. 9. A brachial valve which is broadly flattened in the umbonal region and greatly narrowed anteriorly. 

 The shell has been lost except about the umbo, exposing a portion of the muscular Bears. 

 Oriskany sandstone. Knox, New York. 



