SURIRELLA. 37 1 



i c.d.m. Pseudo-raphe very narrow; stria? rather strong, 10 or 1 1 in i c.d.m. 

 Girdle face linear, somewhat cuneate, with alee very conspicuous. Length, 

 1 5 to 4 c.d m. 



Brackish water. England (W. Sm. ! Kitton, Norman, Greg.). 



S. robusta Ehr. (Mb., 1840, p. ^15; Mikr., pi. 15, f. 43: Suri- 



rella nobilis IV. Sm. ; H.V.H. Atl., pi. 71, f. 1 and 2* ; Type 4(8), plate 12, 

 fig- 577 



Differs from the preceding by its more considerable size, the absence of a 

 hyaline area round the median line, the more robust costa?, the better marked 

 stria?, and by the ahe being approximate to the connecting zone. 



Fresh water. Aid. Lieg, (De Wild.). It is found here and there in Europe. 



var. splendida. (Nov.? spkndida Ehr., Inf. pi. 14, f. 1 ; S. splendtda 

 Kiitz., H.V.H. Atl., pi. 72, f. 4*; Type No. 422), plate 12, fig. 578. 



Distinguished from the type-form by its smaller dimensions and longer 

 costa;, still more approximate to the median line. 



Fresh water. Rather frequent everywhere. 



S. Cafironi Breb. ! is only an anomalous form of the preceding variety. 

 It is characterised by a ridge at the inferior apex of the r?phe, and result 

 ing from a prolongation of the costa?. 



This form is found occasionally mixed with the type-form. 



var. tenera. (S. tencra Greg.; in H.V.H. Type No. 62, rare), 

 plate 12, fig. 579. 



Differs from the preceding by its narrower form and less marked ala?. 



Fresh water. Frahan (Del.), Scotland (Greg.). 



S. Striatula Turpin (Mem. du Mus. d'Histoire Nat., XVI. ; 

 H.V.H. Atl, pi. 72, f. 5* ; Type No. 423), plate 13, fig. 580. 



Valve broadly oval, with costa? robust, distant, about 1 in r c.d.m., reach- 

 ing to the median line ; stria? rather visible, about 14 in 1 c.d.m. Girdle face 

 very cuneate, showing not very robust ala?, quite marginal. Length, 10 to 16 

 c.d.m. 



Marine and brackish water. Hlankenberghe, Antwerp (Scheldt), England (Kitton, Comber, 

 Stolt., Norm.), Ireland (O'Meara), and on all our coasts. 



var. biplicata Grun. (H.V.H. Atl., pi. 72, f. 6*), plate 13, 

 fig. 581. 



Showing a longitudinal plica near the median portion. 



Antwerp (Scheldt. P. Gaut. ). Very rare. 



