14 Shadbolt on New Forms of Diatomacece. 
the spicula of many of the sponges (of which there is a 
goodly proportion), they are of a siliceous character, such 
as the Dictyocha^ and also a form to which my attention was 
directed by Mr. Busk, and which I purpose identifying by the 
name of Bacteriastrum, from Bocxtyi^kx, a stick, and Aar^ov, a 
star. 
By the kind assistance of another of our members, Mr. 
Capron, I am enabled to lay before you drawings of these 
most interesting bodies (of which may be distinguished three 
species), as also of most of the other novelties. 
From the tenuity of their structure the various Bacteriastra 
are better observed without being mounted in balsam ; they 
consist of a central irregular annular portion (not unlike the 
connecting membrane which may be observed in the DiatomecB 
during self- division), surrounded by from eight to twelve rays, 
each many times longer than the diameter of the central por- 
tion, and the construction of these rays affords a good specific 
distinction, viz. 1st, B. furcatum (fig. 1), the marginal rays 
forked ; 2nd, B. curvatum (fig. 2), marginal rays entire and 
curved in one direction ; 3rd, B. nodulosum, marginal rays 
entire, straight, and covered with small protuberances like a 
knotted stick. This last species is by far the most rare.* 
A form tolerably abundant and quite distinct from anything 
I have ever met with from any other locality I propose to call 
Euphyllodium, from ey, and (pvXKov, having somewhat the 
outline of a spathulate leaf (fig. 3). It is characterised as 
follows : viz. valve symmetrical, convex, divided by a median 
rectilinear rib, reticulations of an irregular oblong form, dis- 
posed in regular and elegant curves around centres formed by 
the terminations of the median rib. I have noticed but one 
species, which I have called C. spatliulatum. There was at 
first some doubt in my mind whether this might not belong 
to the genus Cocconeis, but the very distinct appearance of the 
median line, and the absence of anything that could possibly 
represent the inferior valve, which in the latter genus is 
generally (1 believe always) somewhat different from the 
superior one, and likewise the marked character of the outline, 
satisfied me that this supposition was incorrect. It is not 
unlike the aspect of the genus PodosphcBnia, but here again 
there are differences so distinct as to satisfy me that it cannot 
be referred to it with propriety ; for instance, there is no re- 
flexure of the valve, and the markings are not moniliform 
striae, but rather tessellate in character. 
* Since writing the above, T have made out most unquestionably that 
this pseudo-annular portion is a distinct cell, and not a mere annulus. 
