234 



The Irish Naturalist. [Sept., 



PAI.UDESTRINA [HYDROBIA] JENKINSI, SMITH. 



A NEW IRISH SHELL. 

 BY IJONKL E. ADAMS, B.A. 



While at Ballycastle last May, Mr. R. Welch, of Belfast, 

 showed me some shells he had taken in 1893, and also with 

 Captain Fairer in 1896, from my old hunting-ground at the 

 mouth of the Bann, among which were some individuals 

 of an extremely interesting species, and one new to Irelan'd, 

 viz. : — Pahidestrifia (or Hydrobia) Jenkinsi. 



Apart from its being an addition to the moUuscan fauna of 

 Ireland this species has an exceedingly interesting history, as 

 I hope to show. 



In the year 1889, Mr. Jenkins found a colony of shells on 

 the bank of the Thames near Plumstead, which did not appear 

 in an}' of the text-books, and which were quite unknown 

 to himself and his conchological friends. Accordingly he 

 sent a series to the British Museum, where Mr. E. A. Smith 

 pronounced the species not only new to Britain but also to 

 science. However, after seeing a greater number of in- 

 dividuals, Mr. Smith is not certain that the shell is not 

 identical with a West Indian species, Paludma crystallina of 

 Pfeiffer, and Canon Norman is decidedty of this opinion. 

 Mr. Smith points out, however, that the threadlike keel 

 round the whorls of some individuals of our British species 

 differs from the carination of Pfeiffer's P. crystallina var. 

 coronata, which consists of a row of spines forming a corona- 

 tion rather than a carination. 



In 1 891, I came across the shell in dykes at Sandwich, and 

 in that year also, under the guidance of the Rev. J. W. 

 Horsley, I visited the Plumstead locality ; and the next year, 

 with Mr. C. Oldham, of Manchester, I took it in considerable 

 numbers in a small tributary of the Exe, below Exeter, near 

 Topsham. It then occurred to me that in several respects the 

 three localities were similar, and I gathered the following 

 facts. Both Sandwich and Topsham were of considerable 

 importance as trading ports until, roughly speaking, two 

 hundred j^ears ago, when from different causes both subsided 

 in favour of their respective sisters, Dover and Exeter. Two 



