PYXIDICULA OPERCULATA. 



19. 



PEITCHARD Hist. Infus. [ed. 2.] (1841), p. 198, pi. ii, f. 127; [ed. 3.] 



(1852), p. 433, pi. ii, f. 127. 



BAILEY in Amer. Jrn. Sci. Art, XLII (1842), p. 88, pi. ii, ff. 1. la: 

 BRIGHTWELL Fauna Infus. E. Norfolk (1848), p. 36, pi. x, ff. 10-12. 

 HEKTWIG & LESSER in Arch. mikr. Anat. X (1874), Suppl. pp. 103-105. 

 ARCHER in Qrt. Jrn. Micr. Sci. (2) XVII (1877), p. 110 ; in Proc. 



Dublin Micr. Club, III, 2 (1878), p. 228. 



BLOCHMANN Mikr. Thierw. Siisswass. (1886), p. 11 ; ed. 2 (1895), p. 15. 

 PENARD in Rev. Suisse Zool. IX (1901), p. 238 ; Faune Rhiz. Leman 



(1902), pp. 413-414, 3 figs. ; Sarcodines in Cat. Invert. Suisse 



(1905), pp. 81-82. 

 AVERINTZEFF in Trudui S.-Peterb. Obshch. XXXI, n (1906), pp. 



144-145. 



SCHOUTEDEN in Ann. Biol. lacustre, I, 3 (1906), p. 333, f. 4. 

 DOFLEIN in Sitzb. Ges. Morph. Miinchen, XXXIII, 3 (1908), pp. 



116-117, f. 1 (7 figs.). 



WAILES & PENARD in Proc. R. Irish Acad. XXXI, LXV (1911), p. 19. 

 Cyclotella operculata 



? BREBISSON Consid. Diatom. (1838), p. 20. 

 KUETZING Bacill. oder Diatom. (1844), p. 50, pi. i. f. 1 ; ed. 2 (1865), 



p. 50, pi. i, f. 1. 

 MENEGHINI in Atti Impl. Inst. Venuto, V (1846), pp. 88, 90; (transl. 



in) Bot. and Physiol. Memoirs (1846), pp. 385, 387. (Ray Soc.) 



8. London. 



PERTY Kenntn. kleinst. Lebensf. (1852), p. 200. 

 Arcella patens 



CARTER in Ann. Nat. Hist. (13), XIII (1864), pp. 61-62, pi. ii, f. 15. 



(Non Claparede & Lachmann Etudes Inf. et Rhiz. (1859). 



FIG. 164. Pyxidicula operculata : 1, upper view ; 2, side view, x 1200. 

 3, part of the test, x 4800. (After Penard.) 



Test discoid, circular, with narrow inverted margin 

 forming a large circular orifice ; formed of smooth, 

 transparent, chitinous material finely punctate, be- 

 coming darker or nearly brown with age ; plasma clear, 

 granular, nearly filling the test to which it is attached 

 by numerous epipodes ; nucleus single, spherical, con- 

 taining a large central nucleole ; contractile vesicles 

 usually numerous; pseudopodia short, lobose or digitate. 



2* 



