FRESHWATER RHIZOPODS AND HETIOZOA. 319 
A rare species, which I have only obtained copiously from 
Bowness, Westmoreland. 
21. Dirrivera acuminata, Hhrenb. Infus. 1838, p. 131, t. ix. 
£.3; Leidy, l. c. p. 109, t. xiiii—D. bacillariarum, Perty. 
An abundant and widely distributed species, which I have 
observed up to 2200 ft. on Glyder Fach, N. Wales. 
Var. AaMPHORA.—D. amphora, Penard, in Mém. Soe. Phys. et 
d’ Hist. Nat.Genéve, tom. xxxi. no. 2, 1890, p. 189, t. ili. ff. 55-65. 
Not D. amphora, Leidy (which is a variety of D. urceolata). 
Differs from typical D. acuminata in the upper portion of the 
shell being acutely conical but not acuminate. 
This variety frequently possesses a shell consisting of a thin 
chitinous membrane incorporated with Diatoms. Cfr. Leidy, 
l. c. t. xiii. ff. 23-26. Such forms were very abundant from 
Cocket Moss, near Giggleswick, W. Yorkshire, and in all cases 
the Diatom was Vanheurckia rhomboides var. saxonica. 
Var. ELEGANS.—D. elegans, Penard, l. c. p. 140, t. iv. ff. 4-11. 
A small variety with the acuminate apex of the shell tube-like 
and perforated. Length of shell 94-100; breadth of shell 
52-58 »; breadth of mouth 27-31 p. (Pl. 28. figs. 11-12.) 
Wicken Fen, Cambridgeshire. Llyn-y-cwm-ffynov, N. Wales. 
The shells of this variety are generally chitinous, paie yellow 
or brown in colour, and they may or may not be encrusted with 
a variable amount of sand-grains. The body of the animal is 
quite normal, and is supported towards the apex of the shell by 
the usual, protoplasmic, stay-like projections. The actual apex 
of the shell is drawn out into a long tube, which is frequently 
bent at a considerable angle to one side, and the end of this tube 
is open. I have never observed any exudation of protoplasm 
into this tube, the body of the animal being somewhat removed 
from its base. As the shell possesses two openings, one at each 
end, itis quite comparable to shells like Ditrema and Amphitrema, 
which are placed in the family Amphistomina, although in 
the Difflugia only one aperture is utilized for the protrusion of 
pseudopodia. 
Occasionally a few Diatoms are incorporated into the shell, 
and one instance was noticed in which a number of living Diatoms 
were attached to it. 
