72 CATALOGUE OF 



As a rule this species is recognizable at the first glance owing 

 to its quadrangular shape (PI. XXIX, f. 16 a, 23 & 27). In the 

 few instances in which it assumes a rounded exterior and 

 approaches other species in form, it is at once known by the very 

 narrow and fairly straight hinge-line and the slender cardinals 

 which run in the direction of the hinge-line and in the left valve 

 are parallel to each other. 



PI. XXIX, f. 22 shows one of the more rounded forms similar 

 to Jenyns' Pisidium pulchellum, var. 3. 



Fig. 8 on the same plate shows an example whose inflation is 

 a little in excess of the normal, fig. 9 one of maximum inflation 

 and fig. 11 a flattened form. Figs. 10 & 30 illustrate the 

 peculiar variant of the species occurring in the Holocene at 

 Gayfield, Edinburgh, in which the umbones are strangely pro- 

 duced. 



DISTRIBUTION. 



si 

 01 



NS CA 

 HB 88 



RW RE EL BF AN 



Wl El PN AS 



AM PM FF Kl 



M JN SG PC KF 



1 CT RF LL |D HD 



AY LA PE BW NN 



WD ED LD AN WT KB DF SK RX SN 



FJ TY AR DO CU WL NY DM 



WM SL LE MO IM Ml, MY EY 



EM RO CV LH ^ SL WY SY IN 



WG NG LE WH ME M DB FT CH DY NM LS 



SG KC KD DU MN MG SP ST LR CB WH [J 



CL NT QC CW Wl CD RA HF WO WW N HU H 



NX U ST KK WX PB CM BR GE X BX B D HT NE 



SK MC EC WA 6M MM GW NW BK MX S 



WC HS SW NH SR^WK EK 



L ND SS DT SH yvX EX 



EC 80 IW 



SC WC 



Cl 



Pisidium m iliu m . 



(Recent occurrences are shown in red-, fossil occurrences by a line 

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



