310 
Aug. F. Foerste 
at the anterior ends of the four cuneate depressions. The cuneate 
depressions themselves merely indicate the successively advancing 
former locations of these areas of attachment. 
The markings on the interior surface of the pedicel valve may 
be compared most readily with those figured by Hall and Clarke 
(loc. cit. pi. 1, fig. 6) in the case of Lingula procteri Ulrich, from the 
upper part of the Cynthiana group, at West Covington, Kentucky. 
The muscular area extends forward from the beak a distance of 7.5 
mm. terminating at the crest of a crescentic callosity crossing the 
valve transversely near midlength of the shell. From this crest 
the anterior side of the callosity slopes forward for a distance of 
0.6 mm. to the general level of the interior of the valve. Between 
imaginary radiating lines extending from the beak forward to the 
antero-lateral angles of the shell, the muscular area is distinctly 
flattened, this flattened area reaching at its anterior margin a width 
of 4 mm. Along the median line of this flattened area the surface 
is slightly elevated, the nearly obsolete cuneate elevation attaining 
a width of about 0.8 mm. at its anterior margin. The muscular 
area intrudes for a slight distance, beyond the flattened part, upon 
the postero-lateral concave part of the interior of the valve. Vas- 
cular markings extend from the ridge along the top of the crescentic 
transverse callosity forward down the anterior slope of the callosity 
and then along the general interior surface of the valve for a total 
distance of 2 mm. from the apex of the ridge of the callosity, near 
the median parts of the shell, becoming successively shorter laterally. 
Their direction is approximately perpendicular to the curvature of 
the anterior margin of the muscular area. Similar vascular markings 
are found in Lingula vanhornei, a shell having an outline very similar 
to that of Lingula procteri. 
It is not at all improbable that Lingula brookvillensis is closely 
related to Lingula hisulcata Ulrich, from the Economy member of 
the Eden group at Ludlow, Kentucky. Lingula hisulcata is a dis- 
tinctly shorter and broader shell, and the median septum of the 
brachial valve is much shorter. There is, however, a similar gen- 
eral outline. There is also a similar faint elevation of the median 
parts of the exterior of the valve, bounded by faint radiating de- 
pressions on each side, as in Lingula hrookvillensis, but no special 
significance is attached to the latter features since they appear to 
be quite frequent, although often obsolete in various individuals of 
the same species, among the quadrangular forms of Lingula. 
