PLATE LXXV. 



(Figures 1-6 by G. B. Shhpson; 7, i) by F. B. Meek; 9 by E. Emmons. 1 



Genus EENSSEL^RIA, Hall. 



Page 255. 



Renssel^ria Cayuga, sp. uov. 



Figs. 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. 



RENSSELiERlA OVULUM, Sp. IIOV. 



Fig. 3. An internal cast of the brachial valve ; showing the musculai- 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 ami its 

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

 differs from the foregoing in is pei-sistently greater size, much more convex valves, and 

 coarser plication of the surface. It is a more orbicular and more regularly convex shell than 

 R. ovoides. 



Oriskany sandstone. Cayxiga, Ontario. 



RENLSEL.SRIA OVOIDES, Eatoil. 



Tig. 5. 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 posterior divisions 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. SdioJiarie, Neiv Tork. 

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

 muscular impression and the cavities left by the teeth. 



Oi-iskany sandstone. Sj'i'ingpcn-t, Cayuga cowiity, Neio Yoi-k. 

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

 riorly, and 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 plication. 

 Oriskany sandstone. The HeJderhergs, New York. 

 Fig. 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 scars. 

 Oriskany sandstone. Knux, New Tm-k. 



