236 JOURNAI. OF CONCHOLOGY, VOL. 1 5, NO. 8, JANUARY, I918. 



well-marked umbonal striae that occurred in the Wolfhill mill-dam, 

 near Belfast, and the knowledge that P. 7iitidiwi had been discovered 

 in this mill-dam by William Thompson soon after Jenyns's description 

 of the species was published, coupled with the fact that Thompson's 

 specimens had been referred by Jenyns himself to P. nitidiun. Indeed 

 I looked upon the Wolfhill shells as practically co-types of Jenyns's 

 species, and was surprised when similar specimens from other locali- 

 ties which I sent to Mr. Woodward were pronounced by him to be 

 P. pusilluvi, especially as shells which Mr. Woodward referred to 

 P. nitidimi did not accord to my mind with Jenyns's description of 

 that species. I knew that Mr. Woodward had examined Jenyns's 

 type specimens, and my surprise and perplexity grew when I found 

 that the species I always looked upon as P. ju'tidum, but which Mr. 

 Woodward referred to P. pusilhim^ possessed a funnel-shaped siphonal 

 tube with " the aperture very patulous, sometimes plaited at the mar- 

 gin, and more or less crenate," a character upon which Jenyns laid 

 great stress in the diagnosis of his P. nitidu?n. Mr. Woodward in his 

 " Catalogue " attaches great importance to the character of the hinge, 

 and it is noteworthy that the hinge of the clean shining shells that I 

 had always associated with P. nitidum agree with Mr. Woodward's 

 description of the hinge of P. pusillum as understood by him. My 

 doubt as to Mr. Woodward's identification of Jenyns's species grew 

 when I turned to Jenyns's account of their respective habitats, for he 

 states that P. nitidum inhabits "various situations, though seemingly 

 partial to clear water," whilst P. pusillum resides " chiefly at the bot- 

 toms of drains and ditches, where I have often found it living at a 

 considerable depth in the mud," an apt description of the conditions 

 under which live («), the clean shining shell that Mr. Woodward 

 refers to P. pusiliu?n, but which I had been brought to regard as 

 P. nitidum^ and (^), P. personatum. Taking everything into con- 

 sideration I could not escape the conclusion that the P. pusillum of 

 Mr. Woodward was Jenyns's P. nitidum. 



Mr. C. Oldham, with whom I had discussed the subject, was in 

 Bath recently, and took advantage of the opportunity to examine 

 Jenyns's shells in the Museum of the Bath Royal Literary and Scien- 

 tific Institution. The collection includes a drawer of specimens of 

 Sphterium and Pisidium. The shells are mounted on tablets \ no 

 localities are given, but the names are written on the tablets in 

 Jenyns's hand. 



One tablet bears the inscription : — 



"The above are the identical specimens figured in my 'Mono- 

 graph of the British species of Cyclas and Pisidiufn,'' in the fourth 

 volume of the Transactions of the Cambridge Philosophical Society, 

 pll. 19-21." 



