130 CYCLADID^. 



the rest, and most worthy, if any, of separate specific im- 

 portance. We may remark, by the by, that this form is 

 much more likely to prove the Telliua pusilla of Gmelin, 

 derived from Schroter's description and rough delineation 

 of a Hamburg shell (Flussconch. p. 194, pi. 4, f. 7), vtdiich 

 he terms swollen and concentrically striated, than that 

 which we have followed Mr. Jenyns in so denominating in 

 these pages ; but in truth the synonymy of continental 

 Pisidia is so doubtful, that, in default of adequately long 

 descriptions and correctly enlarged drawings of their 

 species, we are unwilling to originate any changes in the 

 nomenclature of our British ones. 



The animal, according to Jenyns, is white : its siphon is 

 polymorphous, short or elongated, cylindric, truncate or 

 obtuse at apex, with an entire or a lacerated margin, vary- 

 ing at various times. 



The largest examples we have seen (kindly lent us by 

 Mr. Thompson) came from Lochnaw in Wigtonshire, and 

 measured two lines and a quarter in length, and one line 

 and three-quarters in breadth. A line and a half by a line 

 and a quarter are the average dimensions of the variety }>. 



In Cambridgeshire it is very common in rivers, ditches, 

 and likewise the smallest streams (Jenyns) ; has been 

 found also in Northumberland (Alder), at Scarborough 

 (Bean), Preston (Sowerby), Battersea Fields and Book- 

 ham Common (var. V) in Surrey (Jenyns), in the ponds and 

 ditches of Northumberland and Durham, not uncommon, 

 (Alder), and at Cadley near Swansea (Jeffreys). 



It is generally distributed in Ireland, remarks Mr. 

 Thompson, " where it inhabits stagnant and running water 

 of the least as well as the greatest extent, and at the same 

 time and place may be found on various subaquatic plants 

 and buried in the mud." The largest and finest specimens 



