New Lamellihranchiata. — Ulrich. 273 
Casts of the interior show an undefined flattening or very shal- 
low depression in the region included between the anterior 
muscle, the basal margin and the umbonal ridge. Anterior 
muscular impression large, deep, subcircular, and roughly- 
pitted. Posterior scar large, faintly impressed, situated near 
the center of the cardinal slope. Shell rather thick, (for this 
genus) and marked with fine impressed concentric stria), in- 
visible to the unaided eye, and stronger lines of growth. 
Length 62.5 mm. ; greatest hight (measuring across the 
posterior third of shell) 29.5 mm. ; hight from beaks to ven- 
tral margin 21 mm. ; greatest convexity of single valve (the 
point is near the middle of the anterior half) 8.5 mm. 
From M. modiolaris Conrad, this species differs in its more 
elongate form, more nearly parallel basal and cardinal mar- 
gins, convex or straight, instead of sinuate basal margin 
greater prominence of umbones, and in being most convex in 
the anterior half of the shell, instead of the posterior. M. 
cincinnatiensis H. and W., with which it is associated, differs 
in its outline and surface markings, as well as in being more 
convex. M. subparallela, of this paper, agrees very well, as far 
as the mere outline is concerned, but it is a much smaller 
species, with the point of greatest convexity near the center of 
the shell instead of in the anterior half, M. pholadiformis 
Kail, likewise agrees very well with this shell, but the peculiar 
divaricating plications which mark the surface of that species 
are so distinctive that there is little danger of confounding the 
two species. 
Position and locality : Utica slate horizon of the Cincinnati group, 
at the Covington, Ky., "river quarries," where it was found associated 
with M. cincinnatiensis and a number of other fossils that are restricted 
to that horizon. 
Modiolopsis subparallela, n. sp. 
Fig. 2. Modiolopsis subparallela, n. sp. Cincinnati group, Coving- 
