50 BRITISH FRESHWATER RHIZOPODA. 



the test is subject to great variation ; whilst figs. 

 1 and 6, PL XLI, show the typical form of each species, 

 individuals of A. seminulum up to 100 /u, or more 

 in length similar to fig. 5 are not uncommon ; also 

 elongated and small-apertured forms of A. muscorum 

 similar to fig. 2, PL XLIII, are occasionally seen. In 

 addition to these normal variations in the form of the 

 test, deformations in the test of A. muscorum are very 

 very common, usually consisting of asymmetry and 

 obliqueness of the aperture. These deformities appear 

 to be due to the desiccation from which this moss- 

 inhabiting species is likely periodically to suffer. The 

 larger species which inhabits moister situations is 

 rarely affected. 



A. muscorum is found in nearly every part of the 

 world wherever moss can grow freely, and flourishes 

 in all latitudes and at all elevations at which mosses 

 are found. A. seminulum is far less ubiquitous, being 

 as a rule restricted to sphagnum growing in pejma- 

 nent pools and marshes. The animals are timid, and, 

 considering the large numbers in which they often 

 occur, active individuals are rarely observed. They 

 are but rarely seen in conjunction. 



SYNOPSIS OF THE BRITISH SPECIES. 



Test modei'ately large ; length 60-100 n or more. 



(1) A. seminulum. 

 Test small ; length 27-58 ju. (2) A. muscorum. 



1. Assulina seminulum (Ehrenberg) Leidy. 



(Plate XLI, figs. 1-5 ; PL XLIII, fig. 1 ; and fig. 131 



in text.) 



Difflugia seminulum 



EHRENBERG in Ber. Akad. Berlin, 1848, p. 379 ; op. cit. 1849, table; 

 Mikrogeol. (1854), pi. xxxv, B, A. ii, f . 1 ; in Monatsb. Akad. Berlin, 

 1861 (1862), pp. 1077, 1102 ; in Abh. Akad. Berlin, 1871, p. 246. 

 PRITCHARD Hist. Infus., ed. 3 (1852), p. 209 ; ed. 4 (1861), p. 553. 

 Difflugia Assulina seminulum 

 EHRENBERG in Abh. Akad. Berlin, 1871 (1872), p. 246. 



