CHAPTER III. 
PARTULA HYALINA Broderip. 
GENERAL CONSIDERATIONS. 
Partula hyalina is taken as the first species to be examined and analyzed in 
detail because it is an unusually distinct form possessing clear differential characters, 
set well apart from the other species of Tahiti. It is distributed widely about the 
island, but varies only in size and shape, so that its study is not complicated by the 
existence of diverse color-types. In one important particular, hyalina is a unique 
member of the genus, namely, in its occurrence in three distinct groups of islands— 
Society, Cook, and Austral—although not in all of the members of any one of these 
groups. This remarkable feature alone would render it of more than ordinary 
interest to the student of its natural history. 
Broderip’s description is dated 1832, thus making the species one of the first 
to be founded after P. faba, the type of the genus, was described by Martyn as 
Limax faba in 1784. The original account of hyalina is as follows: 
“Partula testa oblonga, hyalina, anfractibus sex, longitudinaliter levissime striatis 
et transversim minutissime creberrimeque lineatis; labro albo. long. 9/10, lat. 3/10 poll. 
Hab. in Polynesia (Oheataroa).’” 
The clear hyaline shell (figs. 1 to 13, plate 16) is universally devoid of color, and 
in this respect it is distinguished from all other species of the genus. It is invariably 
dextral. The absence of a pillar tooth is another diagnostic feature, although it is 
shared with other types, such as P. arguta of Huahine. Particular mention should 
be made of the delicate sculpturing of the surface, emphasized by Broderip in his 
original description; the lines of fovee upon the embryonic shell are continued to 
the very limits of the mature and fully formed shell. The aperture is bounded by 
a flaring lip, which is often thickened inwardly, so as to reduce somewhat the size 
of the opening. The plane of this lip, or aperture, is markedly oblique to the axis 
of the shell, as in P. clara, also from Tahiti. Certain other characters are specified 
in the full taxonomic descriptions, such as that of Pilsbry, but the above diagnostic 
features will suffice for our present purposes. In a subsequent section that deals 
with the variation of the shell and with the phenomena of distribution, a more 
detailed description will be given on the basis of the quantitative determinations. 
The following account of /yalina and its natural history is based primarily upon 
the material and observations obtained in Tahiti, which is the only one of the 
Society Islands in which the species occurs. Small collections were also secured in 
Mangaia and Moki, two islands of the Cook Group, where hyalina occurs. It was 
impossible to visit the Austral Islands, where Cuming collected the type forms for 
Broderip’s study and description, in the island named Oheataroa (Oheatoroa of 
Captain Cook) now called Rurutu. It may be possible to secure specimens from the 
last-mentioned locality at a future date, but their lack at the present time is not 
1Proc. Zool. Soc., 1832. 
39 
