An investigation of variation in shell form in Discula (Hystricella) turricula (Lowe, 1831) (Pulmonata: Helicacea)

Submitted by admin on Sun, 20/11/2011 18:56
CHARLES PETTITT
(1977)
Volume
29
Part
3
Page from
147

Measurement of samples of Discula turricida collected over a long span of time from Ilheu de Cima, Porto Santo, indicated that from around 1900 the mean spire height had decreased to a new stable value, the change being accompanied by a temporary increase in variance of shell shape. This change was possibly caused by an alteration in micro-climate following the construction of a lighthouse on the islet in 1900.