248 HELICID^. 



at Plymouth and in Somersetshire, and by myself at 

 Grassmere, Church Stretton, Cardiff, and Tenby. This 

 species belongs to our upper tertiaries. It ranges from 

 Finland to Algeria, as well as to the Archipelago. Von 

 Martens considers it as a southern form, because it retires 

 early into winter quarters; and he remarked that he 

 could not find it in September in a place near Bergen, 

 where he had in the previous summer noticed it in abun- 

 dance and living in company with P. marginata, 



Mr. Alder first indicated that this species is ovo vivi- 

 parous, and recorded the fact in the Supplement to his 

 Catalogue of Land and Freshwater Shells found in the 

 vdcinity of Newcastle. Adolf Schmidt published the same 

 discovery in the ^Zeitschrift fiir Malakozoologie ^ for 

 February 1853; and I can confirm the fact from my 

 own observation. Moquin-Tandon has more than once 

 seen two or three young ones attached to the shell of 

 their mother near the umbilicus and carried about by 

 her — a kind of marsupial arrangement. P. umbilicata 

 reproduces in July and August ; but it does not appear 

 to be prolific, as no more than 5 eggs have been found 

 in the womb at the same time. The epiphragm is very 

 thin and iridescent. Young shells are Trochiform and 

 obtusely keeled, and have a central and rather deep 

 umbilicus. The spire varies greatly in length. A 

 dwarfed, toothless and thin variety is the P. Sempronii 

 of Charpentier. 



This species differs from P. ringens in being more 

 cylindrical and less barrel-shaped, as well as in the form 

 of the mouth and number of the teeth. 



The observant Lister first made known this little 

 land-shell, and the young is probably his Trochus ffyl- 

 vaticus. The present species is the Helios muscorum of 

 Montagu; and it may also be that of Linne, as his 



