54 SHERRIFF TVE : PERIOSTRACUM OF HELIX ARBUSTORUM. 



No. 4 shows the three bands as above, but running from the base 

 of the penultimate whorl towards the umbilicus (i.e., reverse 

 way to the others), the lip dark with its double covering, next 

 ochre lower covering, then shell. 

 No. 5 is var. flavescens just as it occurs in nature. When the 

 two layers of periostracum are present the shell is a dark 

 ochreous colour, when only one, it is a pale lemon, a small 

 spot of the inner coating is removed, showing the white shell. 

 Five of these shells were taken at Lassington, in Worcester- 

 shire; they are very pale. One in my possession has the 

 outer periostracum intact, and gently graduated from the end 

 of the second growth to the finish — a perfect example of 

 a beautiful shell — showing the double periostracum as clearly 

 as it can be seen, and the change of tint due to it. 

 If the last (completing) growth of a shell be dissolved in dilute 

 hydrochloric acid, the periostracum — which is not acted upon by the 

 acid — will plainly show the double layer, under the microscope. 



I do not know whether this peculiarity may be found in other 

 species, I have examined many from various parts of the world but 

 failed to find it. As H. arbustorum has been considered the repre- 

 sentative in Europe of a type having its home in California I turned 

 specially to the species from that part of the earth, but failed to find 

 any indication of a double periostracum, although it is readily seen on 

 every form of H. arbustorum — from every country or locality — which 

 has come under my notice. 



While speaking of this species may I ask if there is a true albino 

 variety ? The var. flavescens is milk-white when denuded of its 

 periostracum — analogous to H. aspersa var. exalbida. I have never 

 seen a shell of H. arbustorum which by any stretch of the imagination 

 could be called white with the periostracum on, though I note 

 Moquin-Tandon gives a var. albina. 



In Science Gossip for August, Mr. Wigglesworth reports taking 

 pink coloured shells of this species — In June last I found pink 

 shells, which I kept on account of their colour, at the Wren's Nest, 

 Staffordshire. The Molluscs were feeding on Coltsfoot (Tussi/ago 

 fa?-fara, L.). Has the plant any influence in giving this colour to 

 the shells? It is known to entomologists that if the caterpillar of 

 the common Tiger Moth (Arctia caia) is fed upon Coltsfoot, it 

 gives rise in the perfect insect to varietal shades of colour in yellow, 

 brown, or black. 



