Description of new Lower Silurian Sponges. — Ulrich. 241 
Marion and Lincoln counties in Kentucky. At those local- 
ities the original material of the sponges, in common with that 
of the associated fossils, has been replaced by silica. In two 
fragments, one from the tops of the Cincinnati hills, the other 
from Spring Valley, Minn., both doubtfully referred to the 
species, the skeleton consists of crystalline calcite. These 
preserve the canals verj'^ well but the minute characters of the 
spicule-fiber are entirely obliterated. 
HETEEOSPONGIA KNOTTI, n. sp. 
Sponges subramose ; branches strong, more or less flattened, 
8 to 20 mm. thick, and 18 to 30 mm. wide. Surface even or 
with irregular swellings. Canal apertures small, sub-equal, 
mostly round, averaging 0.35 mm. in diameter ; arranged in 
rather irregular rows with 6 to 8 in 5 mm. Partitions be- 
tween canal mouths of variable thickness, composed of rather 
compactly interwoven spicule-fibers. Where best preserved 
the angles of junction are prominent. The most distinctive 
feature of the species is found in the oscula which are scat- 
tered over the surface at intervals of from 8 to 20 mm. These 
are nearly circular, about 1.5 mm. in diameter and generally 
surrounded by a variable number of radiating channels. 
Compared with H. subramosa this species will be found to 
differ in having smaller and more closely arranged canals and 
" oscula." The latter are absent in that species. 
The specific name is given in honor of Mr. W. T. Knott, of 
Lebanon, Kentucky, who found the specimens in the upper 
beds of the Cincinnati group near Lebanon and kindl)'^ pre- 
sented them to the author for description. I am also indebted 
to this gentleman for hospitable entertainment. 
HETEROSPONGIA ASPERA, n. sp. 
Sponges of very irregular growth, forming thick, shapeless 
fronds, or strongly nodulated, lobate or subramose, elongate 
masses, several inches in length. When in a good state of 
preservation the surface is remarkably rough, the inter-canal 
spaces being comparatively thin and set at close intervals 
with sharp prominences. The canal apertures are of irregu- 
lar form, often sub-quadrate, and average about 0.5 mm. in 
diameter, with 7 or 8 in 5 mm. They are more regularly ar- 
ranged and of more nearly equal size than usual. The nodu- 
lated examples frequently present areas over which their 
mouths are disposed in a radial manner, bnt there is no 
