48 BRITISH FRESHWATER RTIIZOI'UDA. 



irregularly serrated and surrounded by a four-lobed 

 annular collar; plasma grey, granular, containing 

 Zoochlorella-cells living in symbiotic relationship; 

 nucleus single, large ; one or more contractile vesicles 

 usually present ; pseudopodia numerous, digitate. 



The genus contains only one species, the test of 

 which in general appearance and characteristics 

 resembles that of a Diffluyia, but the collar around 

 the aperture at once distinguishes it. 



There are in reality two apertures to the test, the 

 outer one four-lobed and the inner and smaller one 

 with irregular edges. 



1. Cucurbitella mespiliformis Penard. 

 (Plate LX, figs. 12 and 13.) 



Diffluyia lobostoma 



LEIDY (pars) Fresliw. Rhiz. N. Anier. (1879), p. 114, pi. xv, f. 7. 

 Cucurbitella mespiliformis 

 PENAKD in Rev. Suisse Zool. IX (1901). p. 237 ; Faune Rhiz. Leman 



(1H02), pp. 311-314, 6 figs. ; Sarcodines in Cat. Invert. Suisse (1905), 



pp. 60-61. 

 AVERINTZEFF in Trudui S.-Peterb. Obshch. XXXVI, n (1906), pp. 



176-177. 



SCHOUTEPEN in Ann. Biol. lacustre. I. 3 (1906), p. 340. 

 WAILES in Jrn. Linn. Soc., Zool. XXXII (1912), pp. 124, 133; in 



Naturalist, 1913, p. 146. 



Test ovoid, moderately large, dark grey in colour, 

 composed of variously-shaped silicious grains and 

 plates ; aperture terminal, small, irregularly serrated, 

 surrounded by a three- or four-lobed annular collar; 

 plasma grey, granular, containing Zoochlorella-cells 

 living in symbiotic relationship ; nucleus large, usually 

 containing a large central nucleole which may occasion- 

 ally be divided ; one or more contractile vesicles usually 

 present; pseudopodia numerous, short, digitate. 



Length 116-140 /A; diameter 80-105 /A; inner 

 aperture 15-1 6 /x in diameter; outer aperture 23-33 //, 

 across the widest part ; collar 43-50 /x in diameter. 



Habitat. The ooze of ponds and aquatic vegetation. 

 ENGLAND. Husthwaite near York. 



