222 JOURNAL OF CONCHOI.OGY, VOL. l6, NO. 7, SEPTEMBER, I92I. 



and R. Welch, 24/9/1910) ; and "the upper tarn, in Cwm Glas, at 

 2,475 f^e'^ altitude, Snowdon " (Oldham, 17/7 1916). 



The two above-named species, P. torcjuatum and P. clessi?ii, differ so 

 essentially from all other members of the genus hitherto studied in 

 the anatomical respects mentioned, that I think it justifiable to create 

 a subgenus for their reception, and for which I propose the name 

 Neopisidium, in contradistinction to the subgenus Eupisidium, 

 which would comprise the species with two gills on each side and 

 two siphonal openings. 



Pisidium hibernicum Westerlund, 1894. 

 {P. parvuluin Clessin, 1873, nee Benson ' nee Woodward). 



As Stelfox has stated, the P. parvuhi)n of Clessin is different from 

 P. parvulum of Woodward (1913). In the Stockholm Museum there 

 are some small specimens labelled in Clessin's handwriting " P. par- 

 vulum Cless., leg. Westerlund, Blekinge," which are probably types. 

 They consist of some small and globular examples of P. hiberuieuin, 

 together with two small shells of P. milium. In another box from 

 the same locality (Langasjo, Ronneby), and labelled " /'. parvulum^'' 

 P. hibernieum was found together with obtusale, miliuin, and nitidum ; 

 and a third box contained hibernieum and obtusale. Mr. Stelfox states 

 that he has come to the conclusion " that Clessin's parvulum is this 

 little form oUiibernieuni" Sixxd^ the above statements justify his opinion. 



By the kindness of Prof J. Thiele I had the opportunity to examine 

 a specimen of Clessin's var. niartensi. This specimen appeared to be 

 referable to P. obtusale. The remaining ones, the actual types, could 

 not be sent for examination. 



The distribution of this species seems rather wide (cf. Phillips and 

 Stelfox, 191 8, Schlesch, 1920).^ I have examined the collections of 

 the Swedish State Museum, and it appears that P. hibernicum has 

 been collected in the following districts : — 



Sweden : — Bohuslan : Nordkoster (an island off the coast), some 

 large specimens ; maximum length, 3-1 mm. (Ljungman, 1865). 

 Vastergotland : Surroundings of Boras (Sundler, 191 7). Skane : Lund 

 (Westerlund, det. as obtusale). Ostergotland : Lake Takern, common 

 (N. Odhner, 1908-20, cf. Woodward, 1913). Gottland: Visby, 1879 

 and Eketrask, Faro (Stuxberg, 1867). Sodermanland : Dalbyo, south 

 of Trosa (E. Nordenskiold). Dalarne : Sater (det. by Clessin as 

 obtusale). Harjedalen (N. Odhner, July, 1910) : Sveg, in Ljusnan ; 



o o . 



Lunan, north of Hede ; Flasjon, Ljungan, 13 metres m mud. 



1 Vide Hanley and Theobald, Conchologia Indica, 1876, p. 63. 



2 Phillips and Stelfox : Recent Extensions of the Range of J'isidiutn hiberiiicutn, Irish 

 Natinalist, March, igi8. Schlesch, Pisidium hibernicum Westerlund in Denmark, Naturalist, 

 JNIay, 1920. 



