330 Mr. H. J. Carter on Spicules of Spongilla in the 
Diatomacez in great abundance, the pollen-grains of a Conifer 
(fig. 18, k), the (?) spore-cases of ferns, and the tetraspores of 
an acotyledonous plant (fig. 18, 2), all of which are so recent 
as to be unfossilized. 
When a fragment of this diluvium is broken to pieces in 
water, it soon falls into powder, and then the whole of these 
contents may be examined under the microscope in their 
present state; or it may be boiled in nitric acid, when the 
carbonaceous elements for the most part disappear, and the 
siliceous ones alone remain. 
In the latter state the spicules of the Spongilla, from their 
larger size and great abundance, become the most prominent 
objects, while from their intensely spinous character (fig. 18, 
g) they appear, as before stated,-to be most nearly allied to the 
skeletal ones of Spongilla (Me yenta) ertnaceus, which was 
first found in the river Spree, and described by Ehrenberg 
under this name in 1846 (Monatsberichte der Berliner Akad. 
d. Wissensch. pp. 96-101, ap. Vejdovski). Here, 7. e. in this 
diluvium, they vary in length between 17 and 59-6000ths 
inch, while the spines are “proportionally much longer and 
larger in the short than in the long forms; all these ‘spicules 
are acerate, fusiform, and gradually acuminated at the ends ; 
but the longest only present the usual curve, with a breadth 
in the centre of 3-G000ths inch, exclusive of the spines (fig. 
18, a, b, g). With them there are also a few others that are 
quite smooth, fusiform, and also curved, but abruptly pointed 
at the extremities, therefore probably belonging to another 
species. Again, in two instances I have met with a slender 
birotulate presenting a smooth and slightly curved shaft, 
altogether about 7-6000ths inch long (fig. 18, 4, 7); but in 
no instance have I observed any other form of statoblast- 
spicule, although one might have expected, trom the minute- 
ness of this delicate specimen, to have at least found some of 
the birotulates of Spongilla erinaceus, if the skeletal spicules 
just described had belonged to this species. With the ex- 
ception of some pyxidial frustules among the immense 
quantity of detritus of Diatomacce present, which, if not 
carefully examined, might be mistaken for such statoblast- 
spicules, | have not found the least trace of any thing like 
a birotulate of S. erinaceus, while the slender birotulate to 
which I have alluded only finds its like in the much stouter 
statoblast-spicule of Jeyenia Badley?, Bk., and other species 
of the kind in North America, viz. in the State of Penn- 
sylvania, whence my _ kind ‘friend Mr. Ed. Potts, of 
Philadelphia, has sent me specimens of species which he 
has discovered there, and is now embodying in a Monograph 
