380 On Lingulasma, Etc. — Ulrich. 
pearance of the central region varies considerably, depending 
largely upon the degree of exfoliation. 
This species resembles L. vanhorni S. A. Millar, but has 
the front proportionally wider and less narrowly rounded. 
In that species the valves are also equally convex. L. ohtusa 
Hall has the sides more convex and the beaks more obtuse . 
Formation and locality : This species ranges from the 
middle beds of the Trenton in central Kentucky to about 
fifty feet above low water mark in the Ohio river at Covington^ 
Ky. The best specimens were collected at Bank Lick, several 
miles south of Covington. Specimens of this species are rare. 
The types are in Mr. Charles Schuchert's collection, and in 
the author's. 
lilNGULA BISULCATA, n. sp. 
Fig. 2. 
Compare Lingula huronensis Billings; Geology of Canada, p. 114, fig. 48, 1863. 
Of this species I have seen only a single valve, whether 
the dorsal or the ventral has not been determined. It is of 
sub-pentagonal form, 13 mm. long, and 10 mm. wide. The 
front margin is gently convex with the median portion pro- 
truding very slightly. The anterior angles are narrowly 
rounded into the nearly parallel and faintly convex sides. 
For a short distance on each side of the obtusely pointed 
beak the margin is nearly straight and then rounds with a 
rather narrow curve into the sides. Surface with two faint 
diverging sulci extending from near the beak to points on the 
front margin a little within the angles ; gradually widening 
and deepening, and leaving a faintly convex fold between 
them. The slope to the lateral margins is flat and for a short 
distance from the beak, even a little concave. Concentric 
stride, regular, very fine and crowded on the sides. Over the 
front half very fine radiating lines are obscurely visible. On 
the inner side a thin median septum extends from the beak to 
a point just in front of the middle of the valve where it ter- 
minates abruptly. 
As intimated above this species resembles L. huronensis., 
described by Billings from the Chazy group of Canada, very 
closely, and the doubt that the differences are of specific im- 
portance is not unreasonable. The figures of that species 
show the beaks to be more acuminate, the posterior angles 
more distinct and the median fold narrower than in the Cin- 
