22 BRITISH FRESHWATER RHIZOPODA. 
desmids were believed to be so and were grouped 
together by him as the Bacillaria, a name now 
restricted to a genus of marine Diatomacez. 
While Carter was the first to transfer this minute 
creature from the Diatomacee to the Rhizopoda, 
Hertwig and Lesser were the first to place it in the 
Rhizopoda under its right name, determining it to be 
the same species as the Arcella patens of Carter but 
not of Claparéde and Lachmann. 
It was first recorded as a British species, with 
several other freshwater microscopic forms of life, 
including Heliozoa and other Rhizopoda, by Brightwell 
(1848), and a few years later it was so recorded by 
Pritchard (1852), but, as both these authors placed it 
under the Algz, it was overlooked when the first 
volume of this work was prepared. Doubtless owing 
to its minute size it has since been overlooked in the 
British Isles until it was discovered in the west of 
Ireland, nearly sixty years later than the previous 
record, and enumerated in the tables in the Clare 
Island Report of Wailes and Penard (1911). 
The figures after Brightwell and Pritchard, which 
are slightly enlarged from their coloured drawings, 
must not be taken as accurate representations of this 
species. They are merely introduced to show how some 
of the early naturalists misinterpreted the structure 
of the test. Penard’s observation (see p. 24) may 
explain them. The figures in Brightwell’s work, 
which were drawn by his daughter, evidently from 
the life, give more detail than any previously pub- 
hshed. It is doubtful whether Pritchard’s figures are 
original, as similar ones had before appeared. 
2. Pyxidicula invisitata Averintzeff. 
(Plate LIX, figs. 6-9.) 
Pywidicula invisitata 
AVERINTZEFF in Trudui §.-Peterb. Obshch. XX XI, 11 (1906), pp. 145- 
146, pl. v, ff. 61-64. 
SCHOUTEDEN in Ann. Biol. lacustre, I, 3 (1906), p. 333. 
Brown in Jrn. R. Micr. Soc. 1918, p. 171, pl., ff. 1-4. 
