HELEOPERA PETRICOLA. 141 



larger size and the comparatively-large imbricated 

 scales which cover the entire surface of the test. His 

 examples were obtained from the deep waters of Lake 

 Leman, where one would expect these characters to be 

 better developed than in the Sphagnum of a marsh; 

 hence our British examples, which have been derived 

 entirely from Sphagnum, seem, in comparison, much 

 poorer. There is, however, no reason to doubt that 

 they belong to the variety which Penard appropriately 

 named amethystea. We find that the bright ame- 

 thystine tint is not confined to the variety under con- 

 sideration but is found also in H. lata sp. nov., to 

 be described later. 



3. Heleopera rosea Penard. 

 (Plate XXX, figs. 1 and 2.) 



Heleopera rosea PENARD in Jahrb. nassau. Ver. Naturk. 

 XLIII (1890), p. 71; in Mem. Soc. Geneve, XXXI 

 (1890), 2, p. 166, t. vii, ff. 59-78; Faune Rhiz. Leman 

 (1902), p. 385, ff. 1-3 (p. 386) ; and in Pr. R. Soc. Edinb. 

 XXV, 8 (1905), p. 59 ; LAGERHEIM in Forh. Geol. Foren. 

 Stockholm, XXIII (1901), p. 514; AVERINTZEV in Trudui 

 S.-Peterb. Obshch. XXXVI (1906), 2, p. 256; SCHOU- 

 TEDEN in Ann. Biol. Lacustre, I, 3 (1906), p. 357. 



More robust and broader than H. petricola var. 

 amethystea, and with a semi-circular crown which is 

 sparingly dotted with sand-grains ; the lateral margins, 

 in the lower half, nearly straight down to the corners 

 of the mouth ; the outline of the latter, with its lips 

 of thin yellowish chitine their colour contrasting 

 strongly with the vinous red of the body evenly con- 

 vex. The oral aperture, when directly presented to the 

 eye, narrow, its outline lenticular or linear. The test, 

 examined laterally, about one half the width of the 

 broader surface. It is covered with amorphous scales, 

 loosely arranged ; and the walls are not too dense or 

 deeply coloured, as a rule, to prevent the plasma and 

 nucleus from being seen. The plasma not filling the 

 entire cavity, but generally appearing as a compact 



