60 BRITISH FRESHWATER RH1ZOPODA. 



margin of one side is concave and its outline is seen 

 in two diagonal lines proceeding from the outer 

 corners showing where one lip is bent inwards in the 

 middle. There are two types of neck, one tapers 

 gradually from the test (fig. 133 l-d), the other has a 

 deep notch all round where it joins the test (figs. 133 a 



FIG. 134. Types of apertures of Sphenoderia lenta. x 1000. a. 

 Length of test 52 /tt : N. Yorks. b. Length of test 53 /t : Scourie. 

 c. Narrow view of same. 



and 134). The collar usually appears homogeneous or 

 faintly granular but occasionally faint indications of 

 discs are perceptible on it. 



The nucleus, which is 8 //, to 25 /A in diameter, is 

 finely granular and contains one or two pale nucleoles ; 

 the pseudopodia are not often observed. Conjugating 



a b c d e 



ooQoO 



FIG. 135. Various types of scales of Sphenoderia lenta. x 1000. 

 a. Scale 8 fi diameter from a test 30 p in length : Scourie. b. Scale 

 10 p. diameter from a test 64 /j in length : Scallaway. c. Scale 13 /t 

 diameter from a test 52 /i in length : Pilmoor. d. Scale 10 x 8 /t 

 diameter from a test 52 /t in length .- Donegal, e. Scale 12 x 10 n 

 diameter from a test 55 p in length : Goathland. 



individuals are occasionally seen. Cysts, which are 

 rare, are spherical and about three quarters of the 

 diameter of the test. 



2. Sphenoderia fissirostris Penard. 

 (Plate XLIII, figs. 7-10.) 



Sphenoderia fissirostris 



PENARD in Mem. Soc. Geneve, XXXI, 1, n (1890), pp. 184-185, pi. x, 

 ff. 30-40 ; in Jahrb. nassau. Ver. Natnrk. XLIII (1890), p. 72 ; in 

 Rev. Suisse Zool. YII (1899), p. 14 ; Faune Rhiz. Leman (1902), 



