410 THE ZOOLOGIST. 
“The young shells,” says Gray, when speaking of this 
species,* ‘have a thin lip, with a slight white internal rib,” a 
fact which is apparently unnoted by any other observer, save 
Mr. J. W. Taylor,t who reproduces Gray’s words, though by 
some oversight, unusual with him, he has omitted to name his 
authority. This white internal rib is not, however, of universal 
occurrence in the immature specimens, as evinced by the 
examples before me, and seemingly it is coincident with a check 
in the growth of the mollusk; but when once formed it is 
permanent, and adult specimens will frequently exhibit one or 
two such internal ribs, marking stages of growth, the only 
external indication of their presence being a lighter band of 
colour across the whorl, interrupting the markings when such 
are present, and coinciding with the lines of growth. Strange 
to say that, common as this phenomenon is in the adult forms, 
and almost typical of the species, it does not appear as yet to 
have been recorded. In H. rufescens, Penn., H. Pisana, Mull., 
and H. virgata, Montf., the same thing occurs, and, as far as I 
can judge from a cursory examination, all the Helices, which in 
the adult stage have a thickening or rib within the usually 
unreflected lip, are liable to form two or even three such ribs in 
the course of their growth. In those Helices, however, which, 
like H. aspersa, have a more or less reflected lip when adult, the 
pauses in growth are indicated only by an interruption in the 
markings on the exterior of the shell. 
The amount of variation in the ground colour of the shell 
shown in these Scotch specimens, even in those from one spot, 
is somewhat remarkable. Out of twenty-four specimens collected 
at Rock, near Loch Brora, six adult and ten young ones are of 
the red-brown or rufous type; one adult is nearer the normal 
colour ; one adult and five young belong to the yellow or fulvous 
type; and one adult individual is olive-green speckled with 
yellow, the band corresponding in colour with the ground tint, 
whilst the interior is purplish brown. One of those belonging 
to the fulvous group appears to the naked eye to be of a uniform 
yellowish tinge, the spiral band being pale brown; when 
* Turton’s Manual of Land and Fresh Water Shells of the Brit. Is., ed. 
Gray, 1840, p. 138. 
} Journ. Conchol. ili. p. 244, 
Fees Po ead dah bib # 
aes ern 
