346 
ON THE WANT OF A KNOWLEDGE OF THE ANIMALS OF THE 
GENUS OLIVA AS A MEANS TO THE DETERMINATION OF 
THE SPECIES. 
By F. G. Bripemay. 
Read 8th May, 1908. 
| ABsrRacrt. | 
Tue object of this paper was to urge the importance of an investigation 
of the animals of the genus Oliva, with a view to determining 
what forms might rightly be considered distinct species and what 
varieties only. 
The absence of sculpture on their shells, all forms presenting 
a perfectly smooth surface, and the great variation of colour and 
markings in many of them, rendered it particularly difficult to 
determine some of the species. Even the columella plaits, which 
vary in number in members of the same species, and become more 
or less obliterated by the additional deposits of enamel during the 
growth of the shell, assisted very little in separating the different 
forms; whilst no material change in the form of the shell takes place 
with the growth of the animal, only a thickening of its substance 
by depositions of additional layers of enamel. Hence there would 
always be much doubt and difference of opinion as to species and 
varieties, until some knowledge of the animals assisted in their 
determination. While certain forms, such as O. angulata, Lamk., 
O. porphyria, Lamk., O. Peruviana, Lamk., etc., appeared to leave little 
doubt as to their being distinct species, others, through their numerous 
varieties, in some cases so nearly approached each other as to render it 
almost impossible to determine to which species many specimens belong. 
The colour of the interior in some cases appeared a distinctive 
feature, and varied but little, as in O. ¢sp¢dula, Linn., O. eruenta, Sol., 
O. episcopalis, Lamk., etc. This, however, was not the case in 
the O. erythrostoma, Lamk., group, many varieties of colour and 
shade being found, and the author was inclined to believe that 
O. erythrostoma, Lamk., O. tremulina, Lamk., and O. nobilis, Reeve, 
were but varieties of one species; for, unless the deep orange interior 
of O. erythrostoma were to be considered a distinctive character, he 
could not, after examining a great number of specimens, find any 
reason for separating them. He thought there was room for doubt as 
to O. maura, Lamk., O. tricolor, Lamk., O. elegans, Lamk., O. glandi- 
formis, Lamk., O. leucostoma, Ducl., and O. tigrina, Lamk., being all 
distinct species ; and the same might be said of O. episcopalis, Lamk., 
O. ornata, Mar., and O. cylindrica, Mar. Irregular patches of yellow 
are faintly distributed on many specimens of the O. episcopalis group, 
