OLIVA, Brugitiere. 



PREFACE. 



My object in writing tlie present Monograph on the genus 

 Oliva has been to produce as much evidence as could be 

 procured by the study of one of the largest series of varieties 

 collected together in any genus of marine Mollusca. If, by 

 a close comparison and a study of the affinity existing be- 

 tween the various species, I have collected a series of facts 

 that will prove useful to my fellow-students in the arrange- 

 ment of their cabinets, or will furnish materials by which 

 general deductions may be drawn, my wishes will have been 

 accomplished. In describing as new many forms not hitherto 

 noticed, and in retaining several of the shells which had 

 been rejected as varieties by my predecessors, I have been 

 influenced by special motives. Wherever shells have served 

 to illustrate a line of affinity existing either between species, 

 or more especially where, by introducing certain forms, an 

 unbroken line of affinity could be established, I have not 

 hesitated to avail myself of all the materials at my command 

 required for that purpose. If a different mode of proceeding 

 had been adopted, and if large numbers of moderately dis- 

 tinct forms had been grouped together under generic or 

 subgeneric heads, the result of many careful observations 

 must have been omitted. On the other hand, to have 

 brought forward a considerable number of named subspecies 

 or varieties would have indicated a desire on my part to 

 decide the exact value of specific as compared with sub- 

 specific distinctions, — a decision which I feel myself by no 

 means qualified to attempt. — F. P. Mae rat, 100, Edge Lane, 

 Liverpool.' 



