PLATE LXXV. 
(Figures 1-6 by G. B. Simpson; 7,!) by F. B. Meek; 9 by E. Emmons.) 
Genus RENSSELiERIA, Hall. 
Page 255. 
Renssel^ria Cayuga, sp. nov. 
Figs. 1, 2. Dorsal and ventral views of a specimen which retains most of the shell; showing the tine sur¬ 
face plication and the lenticular form of the valves. 
Oriskany sandstone. Cayuga, Ontario. 
Renssel.eria ovulum, sp. nov. 
Fig. 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 lDedicle-^•alve; showing the filling of the deep muscular cavity and its 
division by the did actor and adductor scars, and the cavities left by the teeth. This species 
differs from the foregoing in i s persistently greater size, much more convex valves, and 
coarser plication of the surface. It is a more orbicular and more regularly convex shell than 
M. oroides. 
Oriskany sandstone. Cayuga, Ontano. 
Renlsel^ria o VO ides, Eaton. 
Fig. 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 Ampliigenia (see plate Ixxiv, tig' 5). 
Oriskany sandstone. SchohaHe, New York. 
Fig. 6. An internal cast of a pedicle-valve having a regularly oval outline, and showing the tilling of the 
musculai' impression and the cavities left by the teeth. 
Oriskany sandstone. Siynngjjoi't, Cayuga county. New York. 
Fig. 7. The exterioi' of a ]‘)edicle-valve, having the characteristic inflexion of the lateral margins ante- 
I'iorly, and showing the tine 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. I'he Helderhergs, 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, exjiosing a poi'tion of the muscidar scars. 
Oriskany sandstone. Knox, New Ycrrk. 
