ISOTELUS, ACROLICHAS, CALYMENE, AND ENCRINURUS 73 
all with free tips, but only the first two pairs of ribs bear me- 
dian grooves ; moreover, the axial lobe narrows posteriorly to an 
acute point which reaches the notch between the free tips of 
the posterior pair of ribs. Lichas cucullus Meek and Worthen 
(Plate XVII, Figs. 4 A,B) is chosen as the genotype. In the 
Waynesville member of the Richmond formation, in Ohio, Acroli- 
chas is represented by Lichas harrisi Miller, and a species with 
coarser pustules is present in the upper part of the Liberty 
member and the lower part of the Whitewater member of the 
Richmond. 
Acrolichas (?) shideleri sp. nov. 
Plate XVII, Figs. 3 A, B 
Two fragments, both interpreted as right free cheeks of some 
Lichad. The general outline is falcate, but along the anterior 
part of the outer margin of both fragments the curvature is 
concave. Along its entire length, this outer margin is coarsely 
striated, the width of the striated border varying from 2 mm. 
near the posterior end of the free cheek to about 5 mm. along its 
concave curvature. Posteriorly, these striae are directed diago- 
nally outward and backward. Along the concavely curved 
part, the striae bend up and down in an evenly concave manner. 
The remainder of the free cheek, in each specimen, is coarsely 
papillated, the apex of many of the papillae drooping diagonally 
downward in a sort of ^Tear-drop” manner. The inner margin 
of the tip of the free cheeks shows coarse striae, similar to those 
along the outer border, but diverging only slightly from this 
inner margin in direction; these striae can be seen only along the 
posterior part of the inner margin, within 4 mm. from the tip of 
the free cheek. 
In one of these two fragments, the lower surface of the free 
cheek was freed from the matrix. This surface is coarsely 
striated with anastomosing lines, and at its proximal end it 
shows the inner limit of the test on the lower side of the free 
cheek. In removing the matrix, the anterior end of the free 
cheek, with its concave outer margin, was broken off. 
