122 BRITISH FRESHWATER RH1ZOPODA. 



be mistaken for it ; very transparent ; ovoid in general 

 outline, compressed laterally, and surfaced with dia- 

 phanous angular scales adhering at their edges, rarely 

 overlapping; the marginal outline often slightly irre- 

 gular from the protrusion of these scales ; mouth 

 narrow, truncated, its margin irregular in outline, 

 generally bordered by a ring of minute irregularly- 

 shaped sand-grains. The plasma as in the preceding- 

 species, not filling the cavity of the test; nucleus 

 normally situated; the pseudopodia few sometimes 

 a single granular pseudopodium only, extending in 

 length to twice the longitudinal diameter of the test. 



Dimensions : Length 95-120 /x (Penard, 170-200 /x). 



In Sphagnum, Dunham, Cheshire ; also near Towyn, 

 Merionethshire, frequently associated with the pre- 

 ceding species. Loch Ness, Scotland (D. J. Scourjield). 



There is little difficulty in distinguishing this species 

 from N. dentistoma Penard when the structure of the 

 test is examined. The mouth of N. vitrsea is never 

 crenulate; its outline might more correctly be described 

 as irregularly dentate, from the prominence of the 

 marginal sand-grains; the oral extremity of the test 

 is more narrowed than that of the preceding species ; 

 but it must be admitted that the relationship of the 

 two is very close. 



16. Nebela tenella Penard. 

 (Plate XXVIII, figs. 18 and 19.) 



Diffl,ugia annulata EHEENBEKG ? in Abh. Akad. Wiss. Berlin,, 



1871 (1872), p. 249, t. iii, 1, f. 19. 

 Nebela ttnella PENAKD in Arch. Sci. nat. (3) XXIX (1893), 



p. 182, t. iii, ft. 8, 9; and Faune Rhiz. Leman (1902), p. 



375, ff. 1-3 (p. 376) (; c/. AVERINTZEV in Trudui S.-Peterb. 



Obshch. XXXVI (1906), 2, p. 253). 



Test small ; its broadly ovoid body terminated by a 

 prominent neck, which is thickened at the extremity in 

 both the broad and narrow lateral views ; compressed ; 

 of chitinous substance and more or less transparent. 



