40 CODE OF NOMENCLATURE. 



CANON XV. The law of priority is to be rigidly enforced in 

 respect to all generic, specific, and subspecific names. 



REMARK. In respect to subspecific names in relation to the law of pri- 

 ority, see beyond, under Canon XXIX. 



CANON XVI. The law of priority is only partially operative 

 in relation to names of groups higher than genera, and only 

 where names are strictly synonymous. 



REMARKS. " While this generalization has not been formally enumerated 

 in the B. A. Rules, it has become practically the general usage of natural- 

 ists. Thorell explicitly adopts it, and indeed it is impracticable to follow 

 any other course, especially in relation to the more ancient names. A time, 

 will doubtless arrive when mutations in the names of the higher groups, par- 

 picularly families, will be as unnecessary as they are undesirable ; but in 

 Zoology that time has not yet come. 



" It should be clearly borne in mind that such changes are only allowable 

 when by mutation of the characters, or through newly discovered facts, the 

 name in question has become glaringly erroneous, or liable to introduce 

 errors or confusion into science. In family names this occurs most often 

 when a genus from whose name that of the family may have been taken is 

 removed from association with the majority of the genera which that family 

 has included, and that genus is inserted in another family which has already 

 a well-established name. Also, when a large number of genera are redis- 

 tributed into families, widely differing in their limits from those in which 

 they had previously been known. In either of these cases the liability to 

 error may be so great as to render a new name desirable. The answers 

 to Query XXIII. of the circular [sent out by Mr. Dallj indicate that a 

 majority of American naturalists concur in this conclusion." (DALL, Rep., 

 P- 27-) 



A good instance of the soundness of this Canon is seen in the several 

 ornithological groups named by Huxley, ending in -gnatha and -morphtz. 

 Many of them were already named groups, more or less exactly recognized ; 

 but the very different bases and definitions given them rendered it desirable 

 that the names also should be different. 



5. Of Names Published Simultaneously. 



CANON XVII. Preference between competitive specific names 

 published simultaneously in the same work, or in two works of 

 the same actual or ostensible date (no exact date being ascer- 

 tainable), is to be decided as follows : 



