LAMELLIBRANCHIA TA. 
337 
Valves regularly convex below, gibbous above and in the umbonal region. 
Beaks at less than the anterior third from the end, moderately elevated 
above the hinge-line. Umbonal slope flattened, giving a slight angularity to 
the shell above and below it, and an oblique truncation to the posterior 
extremity. 
Test thick, marked in the anterior portion by fine, regular concentric 
striae, some of which become elevated into sharp, lamelliform striae, with 
finer intermediate ones on the posterior half of the shell. The characters of 
the interior are well shown in figs. 19, 20, 21 and 22 of plate xlix. 
Three specimens measure respectively 35, 38 and 43 mm. in length, and 
18, 21 and 24 mm. in height. 
This species differs little in size and form from P. ?mda, but is distinguished 
by the fine striae on the anterior portion of the shell, and the finer and more 
subdued character of the lamellose striae on the posterior part. 
Formation and localities. In the soft shales of the Hamilton group, on the 
shores of Cayuga, Seneca and Canandaigua lakes ; at Darien, in Genesee county, 
at York and Moscow, in Livingston county, N. Y. ; also in Hardy county, Va. 
Pal^eoneilo muta. 
PLATE XLIX, FIUS. 25-32. 
Palceone.ilo muta. Hall. Prelim. Notice Lamellibranchiata, 2, p. 8. 1S70. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 49, fig’s. 25-32. 
Shell large, elongate-ovate ; length less than twice the height. General form 
and convexity similar to the preceding. 
Entire surface marked by regular, strong, lamellose elevated striae, with 
very fine, intermediate striae. 
Three specimens measure respectively 43, 41 and 35 mm. in length, and 
24, 21 and 20 mm. in height. 
This species has the form and proportions of P.fecunda, differing principally 
in the character of the surface, which is entirely covered by strong, lamellose 
