MEMOIRS. 
On some FrEsHWATER Ruszoropa, New or LittLte-Known. 
Fascrcuxtus II. On AMPHIZONELLA VESTITA (sp. nov.), 
ACANTHOCYSTIS SPINIFERA (Greeff) and PLAGIOPHRYS 
spH@RICA (Clap. et Lachm.)! By Wuiiiiam ARCHER. 
(With Plates VI and VII.) 
On a former occasion,? I brought before the notice of those 
interested in types of existence so lowly, a series of forms in 
certain groups of Rhizopoda, at once novel to our fresh- 
waters, as well as some of them possessing in themselves a 
considerable interest as connecting links, leading on to their 
more complex and structurally more differentiated marine 
relatives. Having, since then, continued to bestow some 
attention to the subject, I venture to propose to bring for- 
ward from time to time, as opportunity may offer, such 
casual jottings, or accounts of any few additional new forms, 
as good fortune may enable me. 
In bringing forward those I was able to present in my 
former communication, owing to their heterogeneous nature, 
and their positive and negative characters, inter se, I expe- 
rienced a difficulty in endeavouring to put them before the 
reader in anything like a “natural” sequence. In this, and 
any further communications I may be able to make, my diffi- 
culty alluded to is removed, while the disadvantage remains; 
for I must just submit to take them in such order as accident 
and opportunity may present them, irrespective of jany 
mutual affinities ; and indeed, this is the less to be regretted, 
for as yet the freshwater forms, or rather the types they 
represent, are too few, and their characters too negative, to 
be able satisfactorily to relegate them to established Classes 
and Orders. Nor indeed, possibly, do the freshwaters really 
possess forms calculated to fill up the intervals, or lacune, 
between certain therein existent and already recorded repre- 
sentatives. At least, I think matters must remain as they 
are in that regard for some considerable time longer. 
1 Read before the Royal Irish Academy, 12th December, 1870. 
2 «Quarterly Journal of Micrusso;ical Science,’ Vol. IX, N. 8., pp. 250 
and 386, and vol. X, N.8., pp. 17 and 101 
VOL. XI.—NEW SER. i 
