90 AMERICAN JOURNAL 



Subgenus Anisothyris, Conr. 



Paehydon, Gabb, Am. Journ. Conch, iv, p. 198, 1869. 

 Anisothyris, Conrad, lb. vi, extra, published in advance, Oct. 



10, 1870. H. Woodward, Annals and Mag. Nat. Hist. 



ser. iv, vol. vii, p. 104, Feb. 1871. 

 Not Pachyodon, Schum., Essai, p. 139, (as Paxyodon) 1817. 



The nomenclature of this group is somewhat involved. It is 

 a mooted question whether we may rightly alter a name given 

 by an author to correspond with our own ideas of correct spell- 

 ing and derivation. When the derivation is given and the spell- 

 ing is manifestly erroneous it may be quite proper to correct it, 

 even if, by so doing, we reduce the name to the rank of a syn- 

 onym. When no derivation is given and we are left to our own 

 resources to determine the correctness of the name, I am inclined 

 to the opinion that we have no right to change it. Neither 

 Schumacher nor Gabb gave any derivation, and wbile it may be 

 said that it is sufficiently obvious, yet in matters of this kind it 

 should not be permitted to take anything for granted, more es- 

 pecially when such a course is calculated to throw stumbling 

 blocks in the path of study with the sole result of vindicating 

 the suppositious classical learning of the innovator. Such a 

 course is in the nature of an ex j^ost facto law. 



Nevertheless, in the present case I prefer to follow Messrs. 

 Conrad and Woodward in adopting the name Anisothyris, in a 

 modified sense, though I do not justify the proceeding. 



Recent as is our knowledge of the group, several very grave 

 errors have marked the publications upon it. 



Prof. Gabb, in associating it with Isoeardia, was undoubtedly 

 mistaken, a- has been pointed out by Mr. Conrad. It has little 

 or nothing in common with that genus (or family), except the 

 spiral beaks of some of the species. 



The following extraordinary and entirely erroneous statement 

 is made by Mr. Woodward in his paper above quoted : 



" The recent species (of Corbida, Azara, Necera and Cardilia) 

 all have the umbones directed toward the posterior (siphonal) 

 end ; in the fossil species (of Anisothyris ?), on the contrary, the 

 umbones look toward the anterior side. We find also that the 

 cardinal tooth is in the left valve in the recent, and the right 

 valve in the fossil shell, and the socket vice versa." 



After a most careful comparison of the forms comprised under 

 the name Anisothyris with the recent Corbida ovulata, C. crassa, 

 C. nuciformis and three undetermined species from Panama, 

 Japan and China, and with the fossil Corbida "pyriformis, Meek, 

 (Nevada tertiaries), C. gibbosa, Lea (Alabama eocene), C. oniscus, 

 Conr. (do.), and 0. nasida, Conr. (do.), I am prepared to state 



