RECENT MEMOIRS ON FRESHWATER RHTZOPODA. 203 



he hazarded that an increase by constriction as described by 

 him TTiay be at least one mode of increase for Amphitiema 

 as well. 



But supposing G. paludosa, Cienk., to be really amphi- 

 stomatous, and therefore not a Gromia, and holding to the 

 general view and method of classification adopted by Hert- 

 wig and Lesser (with which I would quite coincide), owing 

 to the test of their form being destitute of foreign particles, 

 and in fact " structureless," it could not be relegated to the 

 genus Amphitrema (as yet, indeed, of but one species only), 

 covered as is the test there by foreign particles (though 

 mainly confined to the outer edge). Were, in fact, my con- 

 jucture correct this form would seem then to fall under my 

 own proposed genus Ditrema,i founded for the form named 

 D. jlaviim, to be referred to further on. 



Euglypha ampullacea, Hertwig et Lesser (fig. 7). 

 The test of this form is flask-shaped, drawn out into a 

 neck, length O'OT, breadth 0-04— O'OS; diameter of mouth 003 

 — 0*025 mm. Hexagonal plates comparatively very minute, 

 elongate, arranged in twenty four spirals, gradually becom- 

 ing longer as they come to form the inflated part of the 

 test ; there are often a few irregularly scattered spines. The 

 mouth is beset by twelve " teeth," each sitting upon two of 

 the plates, their outer margin showing two emarginations. 

 (See fig. 7.) 



Cyphoderia truncata, E. Schulze^ (fig. 6.) 

 This form was found in sea water, and indeed in the same 

 gathering as occurred in the author's Platoum parviim. It 

 differs seemingly from the common CypJioderia margaritacea 

 mainly in the straight, not curved, axis of the test, hence the 

 test-opening comes to be exactly transverse to the longitu- 

 dinal axis, not oblique thereto. The contour and size of the 

 test in C margaritacea is well known to be variable, hence 

 the occurrence of a straight form would not, I fancy, 

 be surprising, and would seem to suggest the generic 

 separation thereof from Euglypha on that account, even 

 though the hexagonal plates be so very much smaller than in 

 most Euglyphae, and not drawn out in the longitudinal 

 direction, is scarcely justifiable. In fact, the obliquity of 

 the frontal aperture has its parallel in the much smaller form, 

 and with considerably larger hexagonal plates, Euglypha 

 pleurostoma, Carter.^ 



^ "Minutes of Dublin Micr. Club," in 'Quarterly Journ. Micr. Science,' 

 vol. xvi, p. 3iO, and vol. xvii, p. 103. 



■ Scliulze, loc. cit., Bd. xi, p. 113, t. v, f. 21-22. 



3 'Ann. and Mag. of Nat. Hist.,' 2 ser. vol. xx (1857). 



