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 Diatomaceae. 



While Carter was the first to transfer this minute 

 creature from the Diatomacese 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 Claparede 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 Alga?, 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- 

 lished. It is doubtful whether Pritchard's figures are 

 original, as similar ones had before appeared. 



2. Pyxidicula invisitata Averintzeff. 

 (Plate LIX, figs. 6-9.) 



Pyxidicula invisitata 

 AVERINTZEFP in Tnidui S.-Peterb. Obshch. XXXI, n (1906), pp. 145- 



146, pi. v, ff. 61-64. 



ScHotiTEDEN in Ann. Biol. lacustre, I, 3 (1906), p. 333. 

 BROWN in Jrn. R. Micr. Soc. 1918, p. 171, pi., ff. 1-4. 



