266 ILLINOIS ACADEMY OF SCIENCE 
smaller individual was 16 mm. in larger diameter and 14 in 
the smaller. In the 4 good specimens at hand the submarginal 
ring is made up of 20 plates which are nearly equal in size, 
and much longer than wide. The upper and outer surface of 
the more elevated portion of each of these plates is grooved by 
4 main transverse furrows which divide this part of the sur- 
tace of each plate into 5 subequal transverse ridges. Besides 
these stronger transverse ridges and furrows, the surface of 
the plates is granulose when unworn. The spoon shaped ex- 
cavations in the outer part of the submarginal plates, described 
by Raymond, are not well exposed, being covered by a series 
of small curved plates lying outside the more elevated portion 
of the submarginal plates of which in some places more than 
two are contiguous to a single one of the latter. 
The disk within the submarginal ring is covered with small, 
convex, granulose plates of irregular shape, except in one place 
where the disk may be broken. In one of the specimens a nar- 
row ridge extends from between adjacent submarginal plates 
for a short distance towards the center, but these are not 
thought to belong to the normal structure of the disk. 
This species is rather common in the Orchard Creek shale, 
both north and south of Thebes, Illinois. 
MOLLUSCOIDEA 
BRACHIOPODA 
Lingula ovoides n. sp. 
Plate sf) Pie ®, 
Description: Shell subovate in outline; the lateral margins 
gently convex in the central portion, antero-lateral margins 
1egularly convex, anterior margin broadly rounded, postero- 
lateral margins nearly straight, diverging at an angle of about 
78 degrees. 
Ventral valve moderately convex, the greatest convexity in 
a transverse direction, highest posterior to the middle from 
which the surface slopes rather regularly to the margins, but is 
less convex over the anterior portion; beak rather gradually 
tapering to the subacute apex. Surface marked by rather 
broad, low, concentric lines of growth which in places appear 
slightly lamellose. 
