148 JOURNAL OF CONCHOLOGY. 



A THEORY AS TO THE POSSIBLE INTRODUCTION 

 OF HYDROBIA^ {PALUDESTRINA) JENKINSI. 



By LIONEL E. ADAMS, B.A., Northampton. 



(Read l)efore the Conchological Society, Dec. 7th, 1892). 



Last August (1892) when on a long-to-be-looked-back-upon 

 conchological walking tour with my friend, Mr. C. Oldham, this 

 very local species rewarded our search at Countess Weir, lialf- 

 way between Exeter and Topsham. We were accompanied by 

 Mr. MacMurdo, of Topsham, whose collection of local species, 

 by the way, is well worth a visit. 



Having last year (Sept. 1891) found P. jenkinsi at Sand- 

 wich in a very similar habitat to that at Topsham, and having 

 visited the Plumstead locality, which is also very similar, under 

 the guidance of the Rev. J. W. Horsley, it occurred to me that 

 this similarity might throw some light upon the manner of its 

 introduction into Britain — provided, of course, that it is not 

 really indigenous. 



It is a little curious, that before we actually found the shell, 

 I had remarked to Mr. Oldham how greatly Topsham reminded 

 me of the old-world, sleepy and decayed Cinq Port ; and upon 

 reflection and enquiry the similarity increased. 



Both towns were of considerable importance as trading 

 ports until, roughly speaking, two hundred years ago, when from 

 different causes both subsided in favour of their respective 

 sisters, Dover and Exeter. 



Mr. MacMurdo informs me that in the reign of Henry VIII. 

 two men-of-war, which afterwards fought against the Armada, 

 were built on the spot where P. jenkinsi now flourishes. They 

 must have been vessels of very small draft to have navigated 

 the Exe at all. It appears that in .these times vessels used to 



* On the generic name see Mr. E, A, Smith's presidential address, Q.J.C., vol. vi., p. 336. 



J.C., vii., Jan. 1893. 



