122 Aug. F. Foerste 
Plectambonites curdsvillensis, sp. nov. 
{Plate X, Figs. 15 A, B) 
In the specimens from the Curdsville bed, at Glenn Creek 
Station, in the northwestern edge of Woodford county, the inte- 
rior of the brachial valve is thickened near the anterior and lateral 
margins, the thickening beginning about 2 or 2^ mm. from 
the margin and extending to within 1 mm. of the latter. How- 
ever, between the thickened border and the margin of the valve, 
the shell is much thinner and is traversed, in the same direc- 
tion as the radiating striae, by a series of short, vascular 
grooves, of which about 7 occur in a width of 2 mm. The 
linear callosity adjoining the hinge-area is narrower than in Plec- 
tambonites rugosa, and meets the thickened border, described 
above, rather abruptly. The two median ridges separating the 
two adductor areas usually are prominent and sharp, as in the 
less mature stages of Plectambonites rugosa, although sometimes 
thickened anteriorly. The lateral outlines of the adductor 
areas tend to be crescentic. Six or seven radiating striae 
occur in a width of 1 mm., with every fourth striation slightly 
more prominent. 
Plectambonites plicatellus, Ulrich 23 
{Plate I, Figs. 8 A, B) 
The chief characteristics of this species are its small size and 
coarse radiating striations. The shells attain a width of about 
5 mm., and 5 relatively strong and prominent striae occur in a 
width of 1 mm. The delthyrium is wide, the sides forming an 
angle of 120 degrees; the lower part is occupied by the chilidium, 
and the upper part by the cardinal process of the opposite 
valve. The species is characteristic of the Fulton horizon, at 
Cincinnati, Ohio. 
Journal, Cincinnati Soc. Nat. Hist., vol. i, p. 15, 1879. 
