322 MR. G. 8. WEST ON SOME BRITISH 
27. NEBELA FLABELLULUM, Leidy, in Proc. Acad. Nat. Sev. 
Philad. 1876, p. 118, ff. 6,7; 1877, p. 264; Freshw. Rhiz. N. 
Amer. 1879, p. 152, t. xxii. ff. 8-19. 
Not so abundant as the preceding species; often found amongst 
mosses on dripping rocks. Up to 2700 ft. on Glyder Fawr 
N. Wales. 
28. NepeLa pEenTIStToMa, Penard, in Mém. Soc. Phys. et 
@ Hist. Nat. Genéve, tom. xxxi. no. 2, 1890, p. 162, t. vi. ff. 98- 
100; t. vii. ff. 1-5.—N. crenulata, Cash, in Trans. Manchester 
Micr. Soc. 1891, p. 50, t. ui. £. 18. 
Length of shell 108-113; max. breadth of shell 82-88 p; 
breadth of mouth 36-88 »; thickness 42 p. 
Amongst Philontis fontana in springs at 2700 ft. on Glyder 
Fawr, N. Wales. ‘ 
This species, which is either rare or overlooked, is completely 
different in outward form from J. collaris, the only species with 
which it could be confounded. Except for the mouth, it is a 
perfect oval in shape, and that orifice appears as a chord cutting 
off the narrower end. There is not even the faintest suspicion 
of a neck, and the mouth is considerably wider than in any form 
of NV. collaris. The specific name refers to the nature of the 
mouth, and therein lies the character which at once distinguishes 
N. dentistoma from N. collaris. The mouth of the shell of the 
former species always presents a crenulate appearance, owing to 
the irregular disposition of the small plates composing the shell, 
whereas the mouth of the latter species is perfectly smooth and 
sometimes slightly thickened. The ratio of the breadth of the 
mouth to the breadth of the shell in WV. dentistoma averages 
1: 2:3, whereas in NV. collaris it averages 1 : 2°8. 
29. NeBELA cartnata, Leidy, in Proc. Acad. Nat. Sci. Philad. 
1876, p. 118, ff. 10, 11; Freshw. Rhiz. N. Amer. 1879, p. 154, 
t. xxiv. ff. 1-10.—Difflugia carinata, Archer, 1866; im Qu. 
Jour. Mier. Sci. 1869, ix. t. xx. £. 12. 
Although widely distributed this species is not abundant. It 
is usually found amongst Sphagnum. I obtamed numerous 
examples from some deep Sphagnum-pools at 2200 ft. on Glyder 
Fach, N. Wales. 
