Repoets on the Scientific Results of the Expedition to the Tropical 

 Pacific ln charge op Alexander Agassiz, by the U. S. Fish CoivKvnssiON 

 Steamer "Albatross," from Aug list, 1899, to March, 1900, Commander 

 Jefferson F. Moser, U. S. N., cojimanding. 



II. 



SOME SPECIES OF PARTULA FROM TAHITI. 



a study in variation. 



By ALFRED GOLDSBOROUGII MAYER. 

 (Published by permission of Geo. M. Bowers, U. S. Commissioner of Fish and Fisheries.) 



The .snails studied in this paper were collected in Tahiti hy Dr. H. F. 

 Moore, Ensign C. S. Kenipff, U. S. N., and the autlior daring two visits of 

 the United States Fi.sh Commission Steamer "Albatross" to the Island, 

 from Sept. 27-Oct. 4, and from Nov. 6-13, 1899. 



A great deal has been written concerning the classification of the species 

 of Partiila inliabiting the Islands of the Tropical Pacific. Unfortunately, 

 however, the various species have been distinguished only by inspection of 

 the color, form, etc., of the adult shells ; and no attempt has been made to 

 dissect the young out from the full-grown snails and thus determine, by 

 direct evidence, whether or no the so-called "species" intergrade, and if so 

 to what extent. There can be no doubt that if this method were pursued 

 with all the known varieties and so-called " species " of such variable snails 

 as Partula and Acliatinella, the number of "species" would be much re- 

 duced; and above nil our knowledge of the true relationships of the 

 various forms would become established upon a more trustworthy basis 

 than can be derived from decisions concerning merely the external re- 

 semblance or dis.similarity of the adult shells. A good example of the 

 confusion which hns crept into the synonymy of these species may be in- 

 stanced in the case of Pnrtida otaheitana (Figs. 3-8), where no less than 

 nineteen specific names have been proposed for the various color varieties. 



