STEI.FOX : ON THE MISATPLICATION OF TISIDIUM NAMES. 237 



Mr. Oldham writes of the specimen of P. nitidujii wYxxch. was figured 

 by Jenyns and is indicated on this tablet by the words "Pi. 20, fig. 7:" 



Right valve. Left valve. 



Pisidium nitidum Jenyns { = P. piisiUtini (Jenyns) B. B. Woodward). 



Magnified about 21 diameters. 



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

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



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



"The shell is unopened. The figure is a bad representation of the 

 actual shell, and fig. 8 shows it as flatter than it really is when viewed 

 endways. The shell agrees with several other specimens on a tablet 

 marked '■Pisidiutn nitidu7Ji Jenyns.' The only specimen that has been 

 opened has the entire hinge obscured by the dried-up animal, so that 

 nothing can be deduced from the teeth. The striae are strongest at 

 the place of demarcation between the nepionic and adult shell, and 

 the outline suggests the species that Mr. Woodward refers to P. pusil- 

 lutn, but the nitid character so noticeable in most of the shells so 

 named by him is absent. 



This absence is due perhaps to age and decay. Many of the shells 

 are more or less encrusted with the white salt that is often so trouble- 

 some in shell collections, and it is evident that at some time or 

 another all the shells on this tablet, as well as the type specimen, 

 have been varnished, for older deposits of the salt are discernible 

 under a film of gum-like stuff. 



The umbones are not prominent, are blunt, and not central, the 

 anterior of the shell being somewhat produced. The shells on four 

 other tablets, marked ?iitidiim, are in an equally unsatisfactory condi- 

 tion. In spite of my inability to see the hinge characters, I have 

 little doubt in referring the shell that Mr. Woodward calls P. pusilltitn 

 to the nitidum of Jenyns." 



Of the type specimen oi ]Q\-\y Vis's Pisidium pusilluin Mr. Oldham 

 writes : — " Shell unopened. The rounded outline and silky texture 

 due to very fine striation indicate P. personatum. The specimen 

 matches exactly a long series on a tablet marked ''Pisidium pusillum 



