9i8 PRINCIPLES OF STRATIGRAPHY 



in 1843 ^01* ^ modern gastropod, as a synonym of Clavilithes, pro- 

 posed by Swainson in 1840 for a Tertiary one, and relegated the 

 name Cyrtulus to the Hmbo of dead terms. As the types of these 

 genera are, however, widely distinct, the name Cyrtulus must be 

 restored to its original significance. 



When a genus includes several distinct groups of species, each 

 of which is subsequently raised to the rank of an independent genus, 

 the original name siiould be retained for the group considered 

 most typical by the original author, or corresponding best to his 

 diagnosis. New names must be given to the other groups. Thus 

 the name Clavilithes has been restricted to that group to which 

 the generic characters, as described by Swainson, best correspond 

 (C. parisiensis, etc.), while another group included by Swainson 

 under the same generic name has been separated under the term 

 Rhopalithes {R. nocc, etc.). 



Types. 



A type in natural history is the material used in describing, 

 defining, and illustrating a species or genus, etc. Two kinds of 

 types are recognized — Primary or Proterotypes and Secondary or 

 Supplementary types or Hypotypes (Apotypes). Typical specimens 

 (Icotypes) not used in the literature, but serving a purpose in 

 identification, are further recognized. 



Terms Used for Specific Types. The following terms have 

 been proposed and have come into more or less general use (24) 

 for types of species : 



I. Primary types (Proterotypes). 



a. Holotypes. 



b. Cotypes (Syntypes). 



c. Paratypes. 



d. Lectotypes. 



II. Supplementary types (Hypotypes or Apotypes). 



e. Autotypes (Heautotypes). 



f. Plesiotypes. 



g. Neotypes. 



III. Typical specimens (Icotypes). 

 h. Topotypes. 

 i. Metatypes. 

 j. Idiotypes. 

 k. Homceotypes. 

 1. Chirotypes. 

 IV. Casts of Types (Plastotypes). 



