PARTULINA, SECTION BALDWINIA. 91 



2. Mauian species. 



a. Last embryonic whorl finely zigzag-lineate ; later whorls 

 moderately convex. P. grisea, no. 49. 



a 1 . Last embryonic whorl obliquely striped; later whorls 

 very convex. P. thaanumiana, no. 50. 



3. Oahuan species. P. dubia, no. 51. 



Mr. H. W. Henshaw, of Washington, D. C., well known as 

 a trained and acute observer in several departments of sci- 

 ence, has given the results of his studies upon this group in 

 the following essay. 



OBSERVATIONS ON HAWAIIAN ACHATINELLID^, BY H. W. 

 HENSHAW. 



"Although much has been written upon the Achatinellida 

 of the Hawaiian Islands, comparatively little has appeared 

 upon the habits of any of the species. During the early part 

 of the year 1903 (January- April) the writer enjoyed unusual 

 opportunities for making observations on the three species of 

 Partulina inhabiting the Island of Hawaii, and the follow- 

 ing notes pertain thereto. 



' The peculiar interest attaching to these particular species 

 lies in the fact that they occur only upon the Island of Hawaii, 

 the youngest of the archipelago, that the three are specifically 

 quite distinct from each other, that two of the three are, so 

 far as known, absolutely restricted to limited sections of the 

 northern end of the island, which is much the oldest, and that 

 the third is found outside of this district only rarely. Thus, 

 living in comparatively unoccupied regions and practically 

 without competition, the three species offer an unusually fav- 

 orable opportunity for a study of their habits, and especially 

 of the method of their colonization and dispersal. 



" Upon Oahu, the metropolis of the Achatinellidce proper, 

 there are so many closely- related species, several often crowded 

 into the same area, that the facts relating to habits and 

 means of dispersal are much complicated. An understanding 

 of the manner in which the species of Achatinella form new 

 colonies and of the laws of color variation in the group will 



