DETERMINATION OF GENERIC TYPES, ETC. 25 



A. GENERA FOR WHICH TYPES ARE DESIGNATED OR IMPLIED IN 

 THE ORIGINAL PUBLICATION. 



Too much stress can not be laid upon selecting the type on basis of 

 the original publication. The further one goes from this publication 

 in selecting the type, the more complicated the case usually becomes. 



1. GENERA ORIGINALLY PUBLISHED WITH ONLY ONE SPECIES. "MONOTYPICAL 

 GENERA." 



RULE. A genus proposed with a single original species takes that species 

 as type. 



Thus, X-us 1890, proposed with only one species, albus 1890, retains 

 albus as type, regardless of the number and history of the species 

 which may later be assigned to X-us and regardless of the subdivisions 

 which X-us may later undergo. 



This is the most simple case which can arise, and the principle 

 involved is so self-evident that it needs no argument. It is fully in 

 accord with the practices of systematists in different groups, both in 

 zoology and botany, so far as these workers have endeavored to follow 

 nomenclatural codes, and it is the logical ruling in accordance with 

 the canons of all codes. 



Fortunately a considerable number of genera in all major groups 

 come under this rule. In the generic names given in the present list, 

 about 240 are absolutely and irrevocably tied to a single original spe- 

 cific name by reason of their original publication with a single species. 



Genera of this kind are frequently referred to as " monotypical" 

 Such designation is not entirely free from criticism, since a genus 

 originally published with several species, one of which was definitely 

 designated as type, is also in a certain sense a monotypical genus. 



The following monotypical genera come within the province of this 

 paper: 



List of genera (chiefly nematodes) originally published with a single species. 

 Acanthocheilanema Cobbold, 1870b (dra- AmblyonemaLinstow, 1898 (terdentatum). 



cunculoides) . 



Ancyracanthopsis Diesing, 1861 a (bila- 



Acanthocheilus Molin, 1858 (quadridenta- biota). 



tus). Ancyracanthm Diesing, 1838a, 1839a (pec- 



Acanthosoma Mayer, 1844 (chrysalis). tinatus=pinnatifidus) . 



Acanthi-us Acharius, 1780 (sipunculoides). i Ancyrocephalus Creplin, 1839a (para- 



Acrobeles Linstow, 1877 (ciliatus). doxus). 



AgchylostomaDubini, 1843a (duodenale). Anguillina Hammerschmidt, 1838 (mo- 



Agriostomum Railliet, 1902 (iryburgi). nilis). 



Allantonema Leuckart, 1884 (mirabile). \ Aphanolaimus de Man, 1880 (attentus). 



Allodapa Diesing, 1861a (ti/pica=allo- ApororhynchusShipley,18Q9(hemignathi). 



dapa). Aprocta Linstow, 1883 (cylindrica) . 



Alloionema Schneider, 1859 (appendicu- 

 latum). 



Ar&olaimoides de Man, 1893 (microphthal- 



0- 



