TAYLOR: MOI.I.USCA OF AUnRUICQ, PAS-DE-CAI.AIS. II5 



var. excel plus Hartm. Bouchard-Chantereaux cites Lwincea peregt a 

 and Z. ovata. 



Limncea auricularia (L.). — The sliells collected during Novem- 

 ber in the Audruicq Canal represent the typical form, but one is 

 referable to Limncea acuialis Morelet, a form which may prove to be 

 distinct when its structure has been carefully examined. Bouchard- 

 Chantereaux, in addition to the foregoing species, catalogues L. 

 glutinosa and L. minuta. 



Vivipara COntecta (Millet). — Widely distributed and very com- 

 mon : the specimens found at Ostove in July are clean, olive-green 

 shells, with three narrow, dark spiral bands ; some shells show about 

 fifteen distinct transverse ridges extending from the umbilicus to the 

 angle of contabulation. Specimens from the ditch at Henuin have 

 the green ground overspread by brown. Bouchard-Chantereaux cites 

 this species as Paludina vhnpai'a Lam. 



Vivipara vivipara (L.). — Specimens gathered in July from 

 Audruicq Canal are very clean, medium sized, inclining towards the 

 var. pyramidata, to which one clearly belongs. All are clear, grey- 

 green shells, with three well-marked dark spiral bands ; the operculum 

 of this species is more distinctly pyriform than that of contecta. This 

 species is catalogued by Bouchard-Chantereaux as Paludina achatina. 



Bithynia tentaculata (L.). — Is widely dispersed and very abun- 

 dant ; the specimens found near Fort St. Jean belong to the var. 

 ventricosa Moq., and are very clear and mainly fawn coloured. The 

 var. margi?iata Baudon is also represented in the collection ; it is 

 characterized by the thick white marginal rib to the aperture, a feature 

 which is also present at the termination of each periodic growth in 

 the young. Bouchard-Chantereaux cites this as a very common 

 species under the name of Paludina impiira Lam. 



Bithynia leachii (Shepp.). — Found at Polincove in June, also 

 during November in a ditch at Henuin, and the Audruicq Canal ; they 

 are very translucent and quite characteristic specimens of the var. 

 elongata Jeffr.- This is another species not known to Bouchard- 

 Chantereaux, and an addition to the fauna of the department. 



Valvata piscinalis (Miill.) was found during July near Fort St. 

 Jean, and is locally common. The specimens are mostly of ordinary 

 form, but a few show more or less distinct traces of spiral ridging 

 recalling the American Valvata tricaritiata Say. ; this form has been 

 named var. arcelini Bourguignat, and would appear to indicate a 

 descent from some spirally ribbed extinct species, and is therefore of 

 highest interest. Noted as very common by Bouchard-Chantereaux. 



Valvata cristata (MiilL). — Widely distributed and very abun- 

 dant ; the specimens in the collection are from pools about Ostove, 



