DIFFLUGIA OLL1FORMIS. 41 



covered with variously-shaped small silicious grains ; 

 aperture large, circular, with a narrow collar ; plasma 

 normal ; pseudopodia few, long, digitate. 



Length 50-84 p ; breadth 44-80 p ; diameter of 

 collar 30-50 /x. (Lngerkeim length 59-70 p ; diameter 

 44-68 p.) 



Habitat. Aquatic vegetation. 



ENGLAND. Pilmoor and Gormire, Yorkshire. 



WALES. Bodelwyddan, N. Wales. 



SCOTLAND. Orkney Islands ; Outer Hebrides. 



In addition to tests of average size, a small variety 

 occurs at Pilmoor, about 30 /x in length, similar to the 

 small form illustrated by Lagerheim (figs. 4, 5). 



The test is very similar to that of D. s 

 Penard, but is distinguished from it by the compara- 

 tively smaller aperture which causes the length to be 

 slightly greater than the breadth of the test ; it is also 

 much more variable in size. The dimensions of D. 

 subasqualis are, length 80-82 ju ; breadth about 88 //, 

 (Penard, ' Revue Suisse de Zoologie,' vol. xviii (1910), 

 p. 933). 



Difflugia tuberculata var. minor Wailes. 

 (Plate LXI, figs. 12 and 13.) 



Difflugia tuberculata var. minor 

 WAILES in Jrn. Linn. Soc., Zool. XXXII (1912), p. 124. 



Test of medium size, pyriform, not compressed, 

 composed of variously-sized quartz-grains with an 

 occasional admixture of diatom-frustules ; aperture 

 small, approximately hexagonal, bordered by a pro- 

 jecting lip ; plasma and pseudopodia as in the type. 



Length 74-100 /A; diameter 52-90 /A; aperture 

 23-25 '/x. 



Habitat. Ponds and aquatic vegetation. 



ENGLAND. Windermere, Westmorland ; Pilmoor, 

 Yorkshire. 



The typical D. tuberculata is characterized by the 



