Reports on the Scientific Results of the Expedition to the Tropical 

 Pacific in charge of Alexander Agassiz, by the U. S. Fish Comsussion 

 Steajier "Albatross," from August, 1899, to March, 1900, Coilmander 

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



11. 



SOME SPECIES OF PARTULA FROM TAHITI. 



a study in variation. 



By ALFRED GOLDSBOROUGH MAYER. 



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



The snails studied in this paper were collected in Tahiti by Dr. H. P. 

 Moore, Ensign C. S. Kenipff, U. S. N., and the author during two visits of 

 the United States Fish Commi&sion Steamer "Albatross" to the Island, 

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



A great deal has been written concerning the cla.ssification of the species 

 of Partula inh ' ' ^ ^ ...„ 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 find Achatinella, 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 dissimilarity of the adult shells. A good example of the 

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

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

 nineteen specific names have been proi)osed for the various color varieties. 



