BRIDGMAN: ON THE GENUS OLIVA. 347 
which appeared to the author to connect them to some extent with 
O. cryptospira, Ford, and O. trisans, Lamk. The interiors of these, 
however, differ in colour. 
Some species, which varied much in colour and markings, were 
easily distinguished by some distinctive character, as O. ¢nflata, Chem., 
and O. ispidula, Linn. ; others, however, appeared to vary very 
little, and were determined without difficulty, such as O. splendidula, 
Sowerby. Where well-marked distinctive characters were absent, as 
in the O. reticularis, Lamk., group, an investigation of the animals 
would be necessary ere the species could be settled. 
Some forms less variable than others appeared to present two 
marked varieties: a larger and lighter, and a smaller and darker 
(e.g., O. episcopalis, Lamk., O. cruenta, Sol., etc.). This had been 
noticed by both Lovell Reeve and Marrat, as seen by the illustrations 
in their monographs, but was not commented upon by them. These 
variations might indicate different sexes, or they might be only local 
varieties. 
There was a callus on the columella of O. Peruviana, Lamk., 
var. coniformis, which was not to be found, as far as the author had 
observed, in the type form, and which he thought clearly pointed to 
some difference in the animals. 
Localities might, of course, have an important bearing upon 
species, but the author was unwilling to admit that a difference of 
locality would alone be sufficient to separate them, nor were the 
localities given for the different varieties of forms always to be 
implicitly relied upon. 
