3G4 MR. J. M. BEOWN ON FRESHWATER RHIZOPODS 



DiFFLUGiA CONSTRICTA {Elirenl.) : Le'idy, '•Freshwater Rhizopods of North 

 America,^ 1879, p. 120; Penard, ^Faune rhizopodiqiie c^-c.,' p. 298. 



This appears to be one o£ the commonest and most widely distributed of 

 the genus, occurring in almost all kinds o£ situations. It is very variable in 

 size, ranging from 64 /x, to 100 /a. Its shape, also, is most variable. It 

 always, however, has an obliquely-placed mouth with inverted margin, a 

 swollen posterior fundus^ and flattened anterior end. The test is always 

 covered with stones. 



DiFFLUGiA oviFORMis, Cash, ^Sritish Freshivater Rliizopoda S)' Heliozoa,^ 

 vol. ii. 1909, p. 52, pi. 20. figs. 8-12. (Plate 50. figs. 6, 7, & 8.) 



In Easedale Tarn numerous empty tests occurred belonging to this species^ 

 which was discovered by Cash in ponds at Chelford (Cheshire). The test is 

 somewhat oval in shape, nearly twice as long as broad, with regularly curved 

 outline. Anteriorly it is abruptly truncated by the borders of the wide 

 mouth. Surrounding the mouth is a very prominent collarette, which in side 

 view gives the appearance of a much-thickened rim. The mouth itself is 

 very prominently and regularly 4-lobed (several specimens showed 5 lobes). 

 The lobes are very regularly rounded, and separated by as many pointed 

 prominences, appearing in side view as notches on the collarette. The test 

 is distinctly brownish yellow and opaque, and is covered with irregularly 

 shaped yellow flakes with very distinct brownish cementing substance 

 between, appearing as brown punctated veins traversing the surface of the 

 test. Unfortunately, none of the specimens were active and the characters 

 of the protoplasm were not observed. 



Size 86 yu, long by 45 /^ broad (Cash gives the size as 110 ^ti long by SO fi 

 broad). 



D. oviformis appears most nearly related to D. limnetica, Levander, and 

 D. gramen, var. achlora, Penard. With these two forms it agrees in the 

 characters of the test and in the presence of the collarette, but differs in size 

 and shape and in the shape and lobing of the mouth. 



Po¥TiGULASiA VAS (Leidy) ; Schouteden, in ' Ann. Biol. Lacustre,'' i. 1906, 

 p. 338, note. 



Typical examples of this species^ which is the Dlfflugia pyriformis, var, vas, 

 of Leidy (' Freshwater Rhizopods of N. A.merica '), were found in Esthwaite 

 Lake. Size 150 /x. Dr. Penard (' Faune rhizopodique &c.,' p. 348) describes 

 this form under the name P. spectahilis. 



PoNTiGiTLASiA COMPRESSA {Carter); Cash, ^British Freshivater Rhizopoda 

 8f Heliozoa,^ vol. ii. p. 61. 



In Easedale Tarn, and also in sediment collected near Sheffield, I have 

 found active examples which, while obviously belonging to this species, are 

 sufficiently large and broad to be identified with the form described by 



