GiiEViLLEj Oil New Diatoms, 
23 
aud E, Roger sii. E. radiatus of Bailey is^ indeed^ inter- 
mediate^ but still very far removed from this very minutely 
punctate diatom. The processes are quite conspicuous^ and 
situated very close to the margin. The puncta in the 
centre of the disc are rather larger than the rest^ but soon 
become minute and cover the whole surface with crowded, 
somewhat wavy lines, the wavy appearance being caused by 
the frequent dichotomous division of the lines of puncta. 
Immediately within the margin, and at short intervals, are a 
series of faint, inconspicuous, radiating lines, not longer than 
the processes themselves, which appear dark or light, according 
as they are focussed. They seem to be produced by a 
slight separation of the lines of puncta, the intervening part 
being somewhat thickened and prominent. 
AULACODISCUS. 
Aulacodiscus MacraeanuSj n. sp., Grev. — Processes cylin- 
drical-oblong, terminating inflated portions of the disc, 
which are rough, with large, raised points ; smaller apiculi 
are numerously scattered over every other part of the surface 
except the spaces which alternate with those connected with 
the processes. Diameter '0054". (PL II, fig. 4.) 
Hab, Ceylon ; rare ; Dr. Macrae. 
A slendid species, so like ^. Peter sii in general appearance 
that any diatomist might be excused for passing over it as 
such in a cursory examination. There are, nevertheless, 
very material differences. In the first place, the processes 
are not orbicular, as in A. Peter sii, but cylindrical-oblong. 
In the last-named species they are much nearer the margin, 
and the inflations vastly more prominent and elongated. 
Then there is a great difference in the margin itself. There 
is, indeed, what may, in general appearance, be called a 
double margin in both ; the inner one being a continuation 
of the disc-surface, and striated, and an outer, narrow ring, 
which in A. Petersii has a hazy, punctate character at the 
extreme edge, arising probably from an undulation in the 
silicious structure. Mr. Tuffen West has represented 
this in his figure of Mr. Shadbolt^s Eupodiscus crucifer 
( ' Mic. Trans. ,^ vol. ii, pi. i, fig. 12), which is admitted 
to be identical with A. Petersii. In A. Macraeanus 
this feature is wholly wanting. Then, again, a careful ex- 
amination of a series of A. Petersii shows that the raised 
points on the surface of the disc are confined to the inflations, 
and less conspicuously along the connecting furrows and 
about the umbilicus.^ ^ So far, however, is this from being 
