BPEC1K3 OF PIS1DIUM. 47 



(PI. XIX, f. 15 a) and from Bohemia (PI. XIX. f. 12 a). Both 

 the lust two instances occur in association with an oval form 

 (PL XIX, f. 156 & 12 b) that outwardly resembles P. pusillum ; 

 as also do examples from Church Close, Mortehoe, Devon (PI. XIX, 

 f. 10). 



An approach to P.^ersonatum is seen in some specimens like those 

 from Gt. Gaddesden, Herts (PI XIX. f. 14 & 37 a, b). Trigonal 

 forms recalling P. casertanum in miniature are those from Loutli, 

 Lincolnshire (PI. XIX, f. 25), Button Coldtield, Warwickshire 

 (PI. XIX, f. 2SJ a, 6), and the fossil example from the Holocene 

 of Newbury (PI. XIX, f. 27). 



The amount of inflation varies from the normal as represented 

 in the Longh Pern specimens (PI. XIX, f. 5) to the more tumid 

 forms from Tenhy (PI. XIX, f. 4) or in the direction of compression 

 to that from the Lea Valley (PI. XIX, f. 7). 



DISTRIBUTION. 



si 



01 



NO SS DT SH WX EX 

 EC SO IW 



WC 



Cl 



Pisidium nitidum. 



(Recent occuirences are shown in red: fossil occurrences Ly a line 

 below the symbols. For the explanation of the symbols see p. 20.) 



