108 PROF. G-. S. WKST ON FBESIIWATER EITIZOPODS 



Observations on Freshwater Ehizopods, with some Eematks on 

 their Classification. By G. S. Wkst, M.A., F.L.S., Pro- 

 fessor of Natural History at the Eoyal Agricultural College, 

 Cirencester. 



[Eeadl6thipril, 1903.] 



(Plate 13.) 



Since my first communication to the Linnean Society on the 

 subiect of freshwater Ehizopods, in 1901, I have had the oppor- 

 tunity of examining a considerable amount of material from 

 some of the outlying districts of the British Isles, and several 

 animals of this class have come under my notice concerning 

 which I can find no previous mention. Two of these are un- 

 described species of the genus HyalospJienia, one is a species of 

 Sphenoderia with a prettily constructed shell, and another is a 

 strange nude form referable to Cienkowski's genus Nuclearia. 



Ehizopods are almost cosmopolitan in their distribution, and 

 few animals exhibit a wider range of variation. In many cases 

 it is almost impossible to define clearly their specific difi'erences, 

 and little attention has been given in the past to the study of 

 the variation of the more abundant forms. 



Altitude appears to have little effect on most species of 

 Ehizopods, as they occur in abundance in suitable localities up 

 to several thousands of feet above the sea-level. Leidy*has 

 collected them at 10,000 ft. in the Uinta Mountains ; and I have 

 observed Trinema enclielijs in collections from the Chilian Andes 

 at 11,000 ft. There is apparently no restriction of special forms 

 to alpine or subalpine situations t, although a few species, such 

 as Assulina seminulum and Heleopera petricola, are most frequent 

 in elevated districts, and a few others seem to have a preference 

 for low-lying ponds and ditches. 



In examining a large number of collections from the "West of 

 Scotland, it was noticed that Ehizopods were relatively less 

 abundant in the Outer Hebrides than on the mainland of 

 Sutherland and Inverness. As the collections numbered more 

 than 500, and were fairly representative, this feature, although 



* Leidy, Freshw. Ehiz. N. Amer. 1879, p. 13. 



t This is also fairly evident from the lists of alpine and subalpine Ehizopods 

 recorded from Sweden and Finland by Lagerheim. Cf. Geol. Foren. Forhandl. 

 1902, Bd. xxiii. Haft, 6, no. 209, pp. 471-472. 



