Section 2 



Designation of Nomendatural Types 



RULE 9a. For each taxonomic group (taxon) there shall be designated a 

 ncmenclatural type. The nomendatural type of a class or a subclass is an 

 order, that of an order or suborder is a family, that of a family, subfamily, 

 tribe or subtribe is a genus, that of a genus or a subgenus is a species, that 

 of a species or subspecies is preferably an authentic culture, but it may be 

 a specimen or preparation, illustration or description. 



ANNOTATIONS 



Rule 9a. The type concept has increasingly become the basis for 

 all modern biological taxonomy. When taxa of any rank are divided 

 or united, the use of the nomendatural type concept leads to rational 

 determination of the correct names to apply. Increasingly, stability 

 and rationality in microbiological nomenclature is dependent upon 

 maintenance of adequate type culture collections. 



The directive of Principle 11, which states that for each named 

 taxon there shall be fixed a nomendatural type, is applied in Rule 

 9. The definition given in Principle 11 is: 



A nomendatural type is that constituent element of a taxon to 



which the name of taxon is peimanently attached. 

 The meaning of the phrase "permanently attached" may be illus- 

 trated. The generic name Bacillus is the nomendatural type of the 

 family BaciUaceae. The family name Bacillaceae is "permanently 

 attached" to the name of the genus Bacillus in the sense that there 

 can be no family Bacillaceae that does not include the genus Bacil- 

 lus. As usually interpreted the family Bacillaceae may include not 

 only the genus Bacillus but also such other genera as are regarded 

 as being sufficiently closely related in their characteristics to the 

 genus Bacillus. The placement of Bacillus in Bacillaceae is objective, 

 while the inclusion of any other genus is subjective; it depends on 

 the decision of the student as to whether the other genus resembles 

 Bacillus sufficiently. The genus Bacillus is the permanent element 

 within the family Bacillaceae. 



Similar is the meaning of "nomendatural type" as applied to the 

 type spedes of a genus. In the genus Bacillus the type species is 

 Bacillus suhtiUs, and the generic name Bacillus is "permanently at- 

 tached" to the species Bacillus subtilis. The genus Bacillus may be 

 defined as the species Bacillus subtilis together with such other species 

 as are recognized as having certain characters in common with those 

 of Bacillus subtilis. 



RULE 9b. Designation of the nomenclotural type of a taxon of higher rank 

 than genus. The nomendatural type of a family, subfamily, tribe or sub- 

 tribe, whose name has been formed in conformity with the Rules, is that 

 genus from whose name the name of the higher taxon has been derived. 

 The nomen^-iatural type genus of a family whose name has been conserved, 



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