Description of new Lower Silurian Sponges .— Ulrich. 245 
nois, is larger and has, as its name may indicate, radiating 
canals of very unequal size. 
This species {H.parva) has been known to me for nearly ten 
years as one of the most persistent fossils of the upper or Galena 
beds of the Trenton group in the western states. I met with 
it first at several localities in central Kentucky, and since have 
found it holding about the same horizon in Tennessee, Minne¬ 
sota and Wisconsin. Though a common fossil, good speci¬ 
mens are rare. 
Occasionally we meet with specimens of this or a closely re¬ 
lated species in the middle beds of the Cincinnati group. 
These are a little larger than the Trenton form, the specimens 
averaging about 10 mm. in diameter. This supposed variety 
of H.parva has been found on the hills about Cincinnati 
Ohio, at Colby and McKinney’s in central Kentucky, and at 
Savannah, Ill. Formerly I supposed it might be identical 
with Miller and Dyer’s Microspongia gr eg aria (Jour. Cin- 
Soc. Nat. Hist. vol. i, p. 37, 1878) but its internal structure is 
clearly the same as that of Hindia. Those authors say of 
their species that its structure is “ fibrous or minutely porous, 
and very compact,” and that sections reveal “ needle-shaped 
bodies ” supposed by them to be the spicules. From this it is 
evident that either they are mistaken in their diagnosis or 
they had a very different sponge before them. 
Seven specimens of another supposed variety of H.parva 
were collected from the upper beds of the Cincinnati group 
near Middleton, Ohio. These have the same internal struc¬ 
ture but are unusually small, the diameters of the smallest 
and largest specimens being respectively 3 and 5 mm. 
CYLiINDROCCEliIA, n. gen. 
Sponges free, cylindrical or nearly so, with the lower end 
tapering rapidly to a pdint, or truncate. A central cloaca ex¬ 
tends throughout at least the sub-cylindrical portion. It is of 
tubular or very elongate conical form, widening gradually up¬ 
wards. Walls thick, traversed by irregularly disposed radiat¬ 
ing canals. Very few of these penetrate the thin and compact 
dermal layer which covers both the inner and outer surfaces. 
When the dermal layer is worn away their sub-circular 
mouths appear. Skeleton, apparently very finely porous. 
The specimens are too much altered to admit of determining 
its elemental components. 
