CERION. 175 



by numerous species, with a multitude of local races. South of the 

 larger islands named, if \ve include with Cuba the faunally depend- 

 ent Cayman group and Isle of Pines, but one single species is found, 

 C- uva, of Cura9ao, singularly isolated in characters as well as geo- 

 graphically. Jamaica is without a species; and the genus also fails 

 in the Caribbean chain. 



In the main, each species is confined to some single island, or to a 

 series of adjacent keys or islets ; but there are numerous exceptions, 

 where forms unquestionably conspecific are found on several islands 

 separated by considerable distances. 



The species are subject to a remarkable range of individual and 

 local variation. Thus many species vary from strongly and conspic- 

 uously ribbed to entirely ribless and smooth. In fact this is a 

 common variation, incontestably established by the series we have 

 examined of Cerion dimidiatum, C. columna, (7. regind, C. uva., G. 

 maritimum, C. sagraianum and many other species. Color is equally 

 variable, pure white species varying to heavily brown-mottled, and 

 this not in one, but in many of the species. Absolute size of adults 

 is almost as mutable as in Gypraea ; and occasionally individuals are 

 abnormally shortened by the premature assumption of the features of 

 maturity, giving them a stunted appearance. 



All of these considerations render the study of the species one of 

 unusual difficulty ; and the older authors, unacquainted with the 

 Protean nature of the species, as with the usually restricted range of 

 each, often failed to properly discriminate them. Thus the several 

 volumes of Pfeiffer's Monographic!, Heliceorum Viventium are unreli- 

 able in dealing with many species, especially in respect to geographic 

 distribution. 



An American writer on natural history, Mr. C. J. Maynard, some 

 years ago begun the study of this genus, and to his earliest publica- 

 tion on the subject we owe the first clear statement of some facts of 

 prime importance ; that the Cerions are excessively plastic, and 

 locally modified into a considerable number of species and sub- 

 species ; that the range of some of these forms is excessively limited; 

 and that former authors had failed to discriminate many really dis- 

 tinct species, "lumping" them under a few old names; and finally, 

 that the aperture-armature, or " teeth " of the Cerions are variously 

 arranged, and furnish ground for the division of the genus into sev- 

 eral sub-genera. Mr. Maynard, moreover, has discovered and de- 



