20 
Greville, on New Diatoms. 
provisional. The valve is somewhat opaque, and varies con- 
siderably in size and in relative length and breadth the ends 
are very slightly convex, rounded and inflated at the corners, 
and the sides generally more or less convex opposite the cen- 
tral nodule, very rarely straight. The longitudinal lines are 
curved outwards opposite the nodule, in number about 21 in 
•001", and most exquisitely punctate. The transverse striae 
are fine, and require careful manipulation for their resolution. 
The front view has straight sides and ends, the angles 
rounded. The whole frustule is very solid and compact. 
Amphiprora. 
Amphiprora oblonga, n. sp., Grev. — Large ; front view ob- 
long; wings not deeply constricted; greatest breadth at a 
point about half way between the constriction and the ends ; 
curve of the lateral plates reaching the constriction. Length 
•0060" to -0085". (Fig. 15.) 
Hab, Harvey Bay, Queensland ; Dr. Roberts. 
Here is a large Amphiprora, which I cannot refer to any 
described species, and yet it may be found eventually to be 
merely an extreme aberrant form. Unfortunately, although 
I have seen many examples, I have been unable to fix upon 
any side view as indubitably identified with it. If I knew 
any described species to which I could trace it, even as a 
remote variety, I would gladly do so ; but the very circum- 
stance of this perplexity renders a figure desirable, and I give 
it a provisional name, which may be cancelled whenever its 
relations shall have been conclusively established. Speci- 
mens occur much larger than the one figured, and, conse- 
quently, greatly exceeding in size A. maxima of Gregory, 
with which I was at first induced to compare it. But that 
diatom is very much more broadly truncate, the widest part 
being near the ends and the constriction very deep, whereas, 
in the present species, the widest part is halfway between the 
end and the constriction, and the latter comparatively quite 
shallow. The character of the marginal curve in the two 
species appears to me to be essentially distinct. It would 
require a careful examination, however, of a long series of 
examples of the different species in order to ascertain finally 
how much dependence may be placed on the character to be 
derived from the curve of the lobes. My own impression is 
that a peculiarity exists in the curve of most of the species. 
