84 JOURNAL OF CONCHOLOGY, VOL. II, NO. 3, JULY, I904. 



and Mr. R. D. Darbishire has it from the old reservoir at Bradford 

 (near Manchester), and from the canal at Hatherlow. Mr. J. R. 

 Hardy has in his collection specimens from a reservoir at Gorton, 

 where it was, some years ago, very plentiful, but has since died off 

 owing to the fouling of the waterj also from "Ardwick Pond" where 

 it covered the stones and piles, but this locality is, like some others of 

 those already mentioned, long ago a thing of the past and quite 

 "historic." 



My first acquaintance with this shell dates from 1878, when I came 

 across numbers of very small but well-marked specimens in the River 

 Brock, attached to large stones. The following year I discovered it 

 in abundance on the sides of bridges all along the Preston and 

 Lancaster Canal — which, for the greater portion of its length, is the 

 cleanest canal I know. Whilst collecting along the hanks of this 

 canal I have several times come across little heaps of freshly gnawed 

 shells of Dreissensia amongst the herbage, close to the water's edge, 

 and believe this to be the work of water voles — the only instance I 

 know of this mussel being preyed upon by any animal. From this 

 canal came my finest and most treasured series, collected by my wife 

 at Woodplumpton, in 1888. These are remarkable for their curious 

 and varied abnormality. Some are broad and flat, rounded and 

 bulged posteriorly; others seem to have had — when about half-grown 

 — both valves opened to their fullest extent and fixed there, the gap 

 being afterwards filled up, more or less regularly, with a secondary 

 growth which has left the old edges of the shell projecting as a frill or 

 flange; others, again, are almost globular, or shaped like a beech-nut. 

 As a rule these abnormal specimens are in good condition, even the 

 secondary growth being perfect as to epidermis and coloration. I 

 have never been able to account for the protean shapes assumed by 

 the shells from this locality during this particular season — the colour 

 and markings, too, were unusually vivid in old and young, normal and 

 abnormal alike, much more so than I have ever observed before, or 

 since. One can well imagine that Pallas had some such series of 

 specimens before him when he bestowed the specific name! 



From 1887 onwards I obtained Dreissensia from Cadley Dam, 

 Preston; canals at Tarleton, Droylsden, Ashton-under-Lyne, Clifton, 

 and Ringley ; and from a reservoir at Lowerhouse Printworks, 

 Burnley, where it abounds in thousands on submerged tree-roots. In 

 some of the localities named the increasing pollution of the canals near 

 the towns is gradually killing off the Dreissensia, and where it still 

 survives under such adverse conditions it is difficult to find even a 

 half-grown specimen in fairly good condition — the adults are so eroded 

 and stunted as to be almost shapeless. Mr. B. R. Lucas finds it 

 abundantly in canals at Chester and Middlewich; and Mr. C. Oldham 



