238 JOURNAL OF CONCHOLOGY, VOL. I5, NO. 8, JANUARY, I918. 



Jenyns.' One of these is open and is beyond doubt P. personatutn. 

 The callus is well marked in both valves. Seven unopened shells on 

 another tablet marked ' Pisidium pusilliim Jenyns ' comprise, I think, 

 P. personahim and P. hibernicum. A tablet marked '■Pisidhim pusillum 

 var.' has had all the shells removed. Specimens on a further tablet 

 marked '■ Pisidmm pudlhim'' (with a ? in pencil) are P. casertanum. 

 Shells on four tablets marked ' Pisidinm cinereiim Alder ' are all P. 

 casertanum. Open valves in each series show the hinge characters well." 



Right valve. J> -^ Left valve. 



Pisidium pusilJum Jenyns {—P. personatiim (Malm) B. B. Woodward). 



Magnified about 21 diameteis. 



From specimen in " Hyndman Collection," Belfast Municipal Museum, 

 labelled "P. pusilluin. English. Mr. Jenyns to W.T." 



A.W.S., del. Oct. 1917. 



It will be seen that Mr. Oldham's notes fully bear out my own con- 

 clusions that Mr. Woodward's P. pusillum is that described by Jenyns 

 as P. nitidum ; and that the P. pusillum of Jenyns is the P. persona- 

 him of Mr. Woodward, and also includes forms of the latter's P. 

 casertanufti. I have obtained still further and quite independent 

 evidence which points to the same conclusion. In the collection in 

 the Belfast Municipal Museum are five specimens sent by Jenyns to 

 William Thompson, labelled '■'■ Pisidium pusilhc7n. English. Mr. Jenyns 

 to W.T." These were completely encrusted with a blackish coating, 

 but upon being opened proved to be typical P. personatum. In the 

 same collection there exist two shells labelled "Z'. nitidum. English. 

 Mr. Jenyns to W.T.," and these are typical examples of the shell 

 regarded by Mr. Woodward as P. pusillum. By the kindness of the 

 Curator, Mr. Deane, I have been permitted to make drawings of one 

 shell from each of these historic sets, and these are here reproduced. 



It may be asked what, then, is Mr. Woodward's P. nitidum ? But 

 that is a question to which I can give no conclusive answer. The 

 large diagrammatic figure of his P. nitidum., given by Mr. Woodward 



