50 
Greyille^ on the genus Auliscus. 
This species is in a very unsatisfactory state^ and it may be 
doubted whether specimens have been seen in a really perfect 
condition. Having myself had no opportunity of examining 
many individuals,, I can say but little regarding it. In one 
example now before me^ the puncta are so disposed over the 
entire surface that not the very slightest trace of a line 
of any kind can be perceived. In one specimen figured^ the 
radiating lines are partially visible. In a valve I have from 
Virginia there are comparatively few puncta^ and the 
characteristic lineation is of course conspicuous. The late 
Professor Bailey compared A. punctatus with A. py'uinosus, and 
supposed that it might prove to be a variety of that species. 
He remarks^ however^ that the sparsely punctate basis of 
the one [pruinosus) with the closely punctate surface of the 
other (punctatus) appear to offer a sufficient distinction 
betAveen them.'^ I apprehend that if these two species are 
to be compared at all with each other^ a better criterion exists 
in the totally different character of the punctation. 
Auliscus Peruvianus (Kitton)^ Grev. — Valve circular, 
with close radiating lines of very minute puncta, and a row 
of marginal apiculi; processes very small, each surrounded 
by a circlet of minute apiculi. Diameter about •0039". 
(Fig. 17.) 
Auliscus Peruvianus, Grev. — ^ Trans. Mic. Soc./ vol. x, 
p. 25, pi. ii, fig. 6 (very coarsely engraved) . 
Eupodiscus? Peruvianus ; Kitton, MS., Ealfs, in Pritch. 
Inf., 1861, p. 938. 
Hab. Peruvian and Californian guanos; F. Kitton, Esq., 
Dr. Macrae, C. Johnson, Esq., R. K. G. 
As I have already mentioned in the tenth volume of the 
Society's ' Transactions,' Mr. Ralfs first indicated the re- 
semblance of this diatom in certain of its characters to an 
Auliscus. At first sight it has far more the aspect of a 
Eupodiscus, under which genus it was published. The very 
small processes, the total absence of any umbilical space, and 
the equal manner in which the surface is filled up with what 
appears to be uniform straight lines of puncta, all tend to 
convey the impression of a Eupodiscus. It is not until the 
radiating lines are carefully examined that some of them are 
seen to follow the usual curved and converging course to the 
processes. In other respects the species is distinguished by 
well-marked characters, the most conspicuous one being a 
rather close series of marginal apiculi. A small, irregular 
circlet of more minute apiculi also surrounds each of the pro- 
cesses, and, what I believe has hitherto escaped observation, 
there is on one side of each process a tubercle larger than the 
apiculi^ and at about the same distance. Minute apiculi 
