16 INTRODUCTION. 



types. These plaster of Paris, sulphur, or lead castings, gutta-percha 

 squeezes, or electrotypes are often quite as good as the originals. No 

 models, however, are included, since they are not cast from type 

 material. 



TYPES OF GENERA, OR GENOTYPES. 



In 1897 Schuchert proposed the term genotype for "anj^ typical 

 material of the type species of a genus. ' ' Subsequent^ he, as well as 

 others, applied this term to the selected type species (not upon the speci- 

 mens, as is stated in the original definition) upon which the genus is 

 based. The original definition is undoubtedly wrong, because genera 

 are not based upon particular individuals, but upon species as a whole. 

 In a letter to the writer (January 9, 1905), Buckman suggests that g~eno 

 be prefixed to the primary type terms, thus making a ' ' completely con- 

 gruous series." With this suggestion, the following terms result: 



Genoholotype. — The one species fixed by an author as the type of 

 a genus. 



Genosyntypes. — More than one species are mentioned by authors as 

 the types of a genus, but no one is definitely selected. These may be 

 monotypical or heterotypical. 



Genolectotype. — A species subsequently selected by an author as 

 the genoholotype of a genus, from genosyntypes. 



Some years ago Walsingham and Durrant" proposed a set of similar 

 terms, but as most of them are preoccupied names they are not adopted 

 here. However, to complete this article of definitions, they are here 

 reproduced: 



A genus from its foundation belongs to one of three classes: 



(1) Monotypical (z. e. described from a single species, no other being known; or 

 described from a single specified species with which are associated other species 

 considered to be identical in structure). 



[The word monotype is also in use for printing apparatus.] 



(2) Isotypical (/. e. , described from more than one species, all of which are con- 

 generic). [The term isotype was used by Gill in 1881 with a different meaning. It 

 is denned on a later page.] 



(3) Heterotypical ( ' i. e., described from more than one species, these differing in 

 structure). 



TYPES OF ORGANISMS IN RELATION TO GEOGRAPHIC 

 DISTRIBUTION. 



Mimotvpes {mimic and form): Forms distantly resembling each other, but ful- 

 filling similar functions, and thus representing each other in different faunas; e. g. 

 (1) the Shrews of Europe are mimotypes of the Antechinus of Australia; (2) the 

 Sloths of South America of the Phascolarctidae of Australia, etc. By the use of this 

 term the word "analogue" may be relieved of a part of the burden borne by it. 

 Isotypes (equal or like and form): Forms common to different countries; e.g., 

 „ the Shrews are isotypes in Europe and North America, etc. [Productus pundatus 

 \^md P. semireticulatus are isotypes of different Carboniferous seas.] 



Merton Rules, London, 1896, p. 14. 



