CONTRIBUTIONS TO PALEONTOLOGY. 30 1 



as free for the foundation of a genus after the citation of M'Coy as before.' 

 This is true enough in part. It was free for the foundation of a genus until 

 1853, when Davidson used it for that purpose ; but since 1853 it has never 

 been free." 



This statement that Mr. Davidson used A. tumida for the foundation of 

 a genus may be " unsophisticated" enough to serve the writer's purpose ; 

 but it seems to us that a little explanation may be necessary. Mr. 

 Davidson, in a spirit of conciliation, proposed to retain Spirigera for A. 

 concentrica and similar forms, and to restrict the term Athyris to such 

 forms as A. tumida, A. herculea, etc. ; but the remonstrances of naturalists 

 against the violation of an established rule induced him to abandon 

 Spirigera and adopt Athyris, citing the former as a synonym.* Mr. D. 

 never used the A. tumida as the foundation of a genus in any other sense ; 

 and he himself abandoned the attempted compromise, and subsequently 

 placed A. tumida with A. hercidea under the Genus Merista of Suess, and 

 this was where I foiuid it when I began my investigations upon the 

 species. Does this appear like using it for the foundation of a genus 1 

 Had the A. tumida proved, as it was supposed to be, congeneric with 

 A. herculea (a Merista), would it still have been the type of Athyris 1 

 Certainly so, according to Mr. Billings' reasoning; and I might ask of 

 him whether he knows its internal structure sufficiently to assert anything 

 regarding its true generic place and relations beyond the fact that exter- 

 nally it is similar to Merista, and possesses internal spires 1 But whether 

 these spires are similar to A. concentrica or to Meristella, as illustrated 

 by the writer, remains to be proved. 



It is, perhaps, not worth while to follow in detail the arguments of 

 Mr. Billings. The rules of nomenclature cited by him seem to be opposed 

 to his arguments, particularly the following : 



"A generic name should always be retained for that portion of the original 

 genus which was considered typical by the author." 



Now what is the typical portion of the genus in this instance 1 Mr. 

 Billings talks of the typical figure, which is given without a name, and 

 therefore impossible of reference. We think there is another rule, which, 

 if not as concisely expressed as that above, is nevertheless usually followed, 

 and this is that where the author neglects to indicate the type of his 

 genus, the first described species under it shall be taken as the type. 

 Mr. B. cites some observations preceding the rule quoted above, which 



* See Note on pages 304 and .305. 



