114 JOURNAL OF CONCHOLOGY, VOL. l6, NO. 4, AUGUST, I920. 



the presence of thickened, former apertural margins and the prob- 

 ability of a thickened termination to the shell mouth being formed 

 when growth was fully completed. Bouchard-Chantereaux describes 

 this species as very common, and also catalogues PL hispidus, PL 

 imbricaius, PL. cristatus and PL compress us. 



Aplecta hypnorum (Drap.). — Gathered in July from pools at 

 Ostove ; they are pale and very glossy shells. Bouchard-Chantereaux 

 records this as very common in flowing water. 



Physa fontinalis (Drap.) is restricted in range though common 

 where it occurs ; the specimens in tlie collection are from Polincove 

 and from the ditch at Henuin, and are chiefly var. obLonga, with a 

 single shell belonging to var. ififlata. Bouchard-Chantereaux says it 

 is common. 



Physa acuta (Drap.) — Local, but common where it occurs ; 

 numerous fine specimens during November in the Audruicq canal. 

 Apart from size and shape, a good distinguishing character is the 

 outline of the deposit of the inner lip, which is also an index to the 

 amount of development of the mantle-margin. This species, which 

 is new to the department, would appear to be somewhat capricious 

 in its development or appearance, as Mr. Cribb had several times 

 previously closely searched the identical spot where the species 

 abounded during November, without noticing any sign of its presence. 



Velletia lacustris (Drap.) is represented by fairly fine, though 

 much encrusted specimens collected in November from a ditch at 

 Henuin, but it is also present in the Audruicq Canal. Bouchard- 

 Chantereaux catalogues the present species, and also Ancyhis 

 fluviatilis and remarks that the examples of this latter species 

 found in river Wimille are of enormous size. 



Limnsea stagnalis(L.).— Found in June in the Audruicq Canal ; 

 they are the ordinary form, and offer no special features. Cited as a 

 very common species by Bouchard-Chantereaux. 



Limnsea palustris .(Drap.).— Rather dwarf specimens of this 

 species, found during June in the Audruicq canal, are ashy-brown in 

 colour, with usually a strong purple submarginal thickening inside the 

 aperture ; they are the var. corviformis Germain. 



Limnaea peregra (Miill.). — Mr. Cribb remarks that though 

 widely distributed, it is not by any means so abundant and variable 

 as it is in England, and this is also apparently true for most of North 

 Central Europe, in which region L. auricidaria is more prevalent. 

 Representatives collected in November from the Audruicq Canal are 

 referable to thevars. ovata Drap., microcephala Cless. and dickinii= 

 major Kob. The shells from St. Pierre belong to var. mnpulLacea and 



