44 BRITISH FRESHWATER RHIZOPODA. 



Wallich in -1864 gave the name Difflugia marsupi- 

 formis to the spined forms of this species and the 

 name D. cassis to the small and usually spineless 

 forms; since then, however, both forms have usually 

 been grouped together under the name D. constrida 

 (Ehrenb.) Leidy. 



In the Clare Island Survey report Penard* has the 

 following note: "In reality these two Khizopoda 

 (Difflugia conxtrlcta and Guntropyxi* aculeata] are 

 practically inseparable ; and in my opinion it would 

 be better to transfer Difflugia constricta at once to the 

 genus Gentropyxis, which, by its peculiar shape and 

 the special disposition of the peristome, etc., is removed 

 from all the DifflugisB." 



Genus 18 a. BTJLLINULA Penard, 1911. 



Bulinella PENAED in Jrn. R. Micr. Soc. 1907, pp. 274, 278. 



(pre-occupied in Mollusca, 1891.) 

 Bullinula PENARD in Brit. Antarct. Exped. I, Biol., 6 (1911), 



p. 226. 



Test smooth, ellipsoidal, flattened on one face, 

 formed of silicious plates cemented upon a thin 

 pellicle ; the flattened face pierced by an elongated 

 narro\y slit constituting a peristome with a smooth 

 inferior lip and an overhanging superior lip ; nucleus 

 single ; pseudopodia digitate or spatulate, simple or 

 branched. 



The genus contains only one species, B. indica 

 Penard, which is widely distributed throughout the 

 world but does not usually occur very numerously. 

 As in the genus Plagiopyxis, the aperture is often diffi- 

 cult to detect and the opacity of the test prevents 

 observation of the plasma. The name Bulinella, being 

 occupied in another Phylum, was altered to Bullinula. 



* Wailes & Penard in ' Proc. Roy. Irish Acad.' Clare Isl. Survey, Pt. 65 

 (1911), p. 22, note. 



