t> OLIVID.E. 



In 1850 Mr. L. Reeve, in his ' Conchologia Iconica,' pub- 

 lished the figures of 100 species, but without any attention to 

 their affinity to each other, and with scarcely sufficient care to 

 the more important part of the shell on which the separation 

 of the species depends. They are therefore infei'ior to those of 

 M. Duclos. 



I believe that it is the uncertainty with regard to the number 

 of the species that has rendered these shells, which are cer- 

 tainly among the most beautiful in form, colour, and marking 

 that we possess, so little attended to by the general collector. 

 This is the more remarkable, as the shells are very extensively 

 distributed over the globe and are easily collected, and therefore 

 procurable by the conchologist at a moderate rate. Though it 

 is very difficult to define the limits of many of the species on 

 account of the great variation in the colour, and the extraordi- 

 nary manner in which the marking gradually changes in its 

 character, yet other species are easily distinguished. 



All the species are easily separated into very distinct groups, 

 defined by variations in the form and structure of the shell, 

 which are evidently produced by important modifications in 

 the structure of the animal. To point out these groups is the 

 object of this List, for I believe that by dividing the species, 

 or varieties which have been considered as species, into such 

 groups, I shall do much to disentangle the subject, and at least 

 confine the confusion to definite limits ; for if the groups are 

 properly defined, it is only the specimens belonging to one of 

 these groups that can be varieties of each other. 



M. Duclos, in his monograph, divides the species into four 

 groups : — 1. Ancilloides (twenty-nine species) ; 2. Cylindroides 

 (fifty species) ; 3. Glandiformes (seventeen species) ; 4. Volutelles 

 (seventeen species). 



M. D'Orbigny, in his ' Voyage to South America,' formed 

 M. Duclos's four sections into three genera, giving to the first 

 section the name of Olivina, to the second and third sections 

 that of Oliva, and to the fourth Olivancillaria, apparently 

 foimded on the form of the animal ; but it is only necessary to 

 compare his figures of the animals of the two species of the 

 latter genus to show how little he attended to his own characters. 



In the ' Zoology to Capt. Beechey's Voyage ' I divided the 

 genus into two, according to the structure of the animal, viz. 

 Oliva and Agaronia, and observed that some Olives were furnished 

 with an operculum not present in other species. More lately, 

 in the text to Mrs. Gray's ' Figures of Molluscous Animals,' and 

 in the ' Guide to the Collection of Mollusca in the Museum,' I 

 have extended the number of genera to four ; separating the 

 operculated Oliva under the name of Olivella, and giving to an 





