The three extensive families of mollusks monographed in this 

 volume of the Manual of Conchology, include several of the 

 most beautiful of the marine genera. The material upon the 

 stud}' of which I have based my text is unusually ample, enabling 

 me to make numerous satisfactory adjustments of the sjnionymy, 

 and to illustrate many variations in addition to the t3'^pical forms 

 of the species. It is hoped that the figures will enable naturalists 

 to identify their specimens with facility and certainty. Excep- 

 tion has been taken to some of the figures heretofore published 

 in this work, on the ground that they are uncharacteristic in 

 drawing and coloring : these illustrations are faithful copies of 

 the original (or typical) figures, such as I almost invariably give, 

 if published; and they are supplemented, whenever it is possible 

 to do so, by better illustrations of the same species. 



The next volume of the Manual will be devoted to the im- 

 portant group of the Toxifera — including Cancellaria, Terebra, 

 Conus, Pleurotoma. Towards its completion 1 again ask the 

 kindly aid of authors and collectors, who may possess nnfigured 

 or critical species. 



January, 1883. G. W. T., Jr. 



