TURBININ^E. 189 



of those subgenera in which this organ is unknown, in order that 

 their correct systematic position may be confirmed. More especially 

 is it necessary that in the cases of Cyclocantha and other groups 

 where the testimony of different observers is considerably at variance, 

 additional species be investigated. 



In the following account of the various species, subgenera and 

 genera of this family, I have taken every care to adopt a nomencla- 

 ture that will prove stable ; deviating in many instances from the 

 usage of previous authors upon this family in order to attain this 

 end. Notably is this the case in certain subgenera of Astralium, in 

 which the pernicious practice followed by many systematists of select- 

 ing what they believe to be a " natural" type for a group, instead of 

 restricting the group to species with the organization of the " histor- 

 ical " type, has led in some instances to the exclusion from a subgenus 

 of the very species designated by the describer of that group as its 

 type ! I have quoted polynomial or "historical" synonymy only in 

 cases in which such names have been adopted into general use. 



In describing sculpture, I have usually avoided the use of the term 

 " transverse," because there seems to be considerable confusion in the 

 minds of many as to whether such sculpture is transverse to the 

 whorls or to the axis of the shell. The term " longitudinal " is here 

 used to designate markings parallel to the axis, and " spiral " to de- 

 note such as follow the direction of the whorls ; in flattened species 

 the former is frequently designated as " radiating," and the latter as 

 " concentric." 



The Turbines have an old and extensive literature. Most of the 

 more prominent species were figured by Chemnitz, and before him 

 by Lister, Rumphius, Knorr, and many another quaint old author, 

 whose tomes now stand undisturbed on our library shelves, as per- 

 haps our own will rest a century hence. From these store-houses 

 Linnaeus drew freely in his mammoth task of cataloguing all animate 

 nature, fitting the species defined by previous authors into his Systema 

 with no other addition than a binomial appellation. 



In modern times each of the four principal monographic works 

 have considered this group : 



Conchy lien Cabinet, monograph by Philippi, 1846-8, 18 . 



Conchologia Iconica, Reeve, 1848, 1861. 



Coquilles Vivants (Kiener), text by Dr. Fischer, 1873, 1880. 



Thesaurus Conchyliorum, Sowerby Jr., 1886. 



