AULISCUS. 
Atdiscus Peruvimius {Kiitoii) , Grev. — Valve or])icular_, with 
close^ radiating lines of fine pmicta^ some of them curved 
and converging towards two small^ fiat, circular, submarginal 
[)rocesseSj each of which iy surrounded by a circlet of minute 
apiculi ; the margin is furnished with a close roAV of larger 
apiculi. Diameter '00S9''. (PL ll, fig. 6.) 
Hab. Peruvian guano, Dr. Macrae. 
The genus of this diatom is considered doubtful by my 
friend, Mr. Rails, who remarks (' Pritch. Infus.,^ p. 938) 
that it has some resemblance to an Auliscvs, but that the 
puncta are not in flexuose lines. Fine specimens, however, 
which have come under my own observation, really confirm 
Ml'. Ralfs' first impression, having the centre connected 
with the processes by a rather narrow band of curved lines, 
not very conspicuous certainly, on account of the fine puncta. 
These curved or converging lines, taken in connexion with 
the imperforate, discoid processes, lead me to follow^ out 
Mr. Ralfs^ indication, and to refer it without question to 
Auliscus. The species is well marked by the numerous 
marginal apiculi and circlet of minute ones which surround 
the processes. A few^ inconspicuous tubercles or apiculi are 
also scattered over the surftice of the disc, wdiieh in a favor- 
able light appear as diaphanous points. 
BIDDULPIIIA. 
Biddidphia pidchtila, Gray. — (PI. Ill, figs. 3, 4.) 
In a gathering obtained by Dr. Macrae at Point de Galle, 
Ceylon, Biddidphia pulchella occurs in the greatest abundance, 
and in every stage of development. No better opportunity 
could be afforded for studying the species, and the propriety 
is at once perceived of uniting the B. trilocidaris, qidnqae- 
/ocularis, and septemlocidaris of Kiitzing, as was done by the 
Jate Professor Smith. In the above-mentioned gathering, how- 
ever, certain frustules sparingly present themselves, which 
differ so considerably from the ordinary state of the species 
that I have considered them deserving of illustration. They 
are trilocular, but will not be confounded with the usual trilo- 
cular state which is most characteristically figured in Smithes 
^ Synopsis^ (pi. xliv, fig. 321). The latter, I need scarcely 
observe, constitutes the m^ost simple form of the diatom, and 
is smaller than the quinquelocular or septemlocular frustules. 
