PARTULA GIBBA, GUAM. 61 
It is in the vicinity of Agafia that it is found in cool places and on the branches 
ertne. trees. . 
Under the name of Partula masterst, in 1857 Pfeiffer described! a series of 
specimens of gzbba which had been collected in Guam by Cuming. The diagnosis is 
very general and gives no reasons for excluding the shells in question from Férussac’s 
gibba. The colors are given as “buff, fleshy, or violaceous, sometimes banded with 
brown on the upper whorls.”’ “Peristome . . . . white or fleshy-brown.” A variety 
is distinguished on the basis of violaceous color on the last whorl, and by a small, 
white, deeply placed tooth within the penultimate whorl. ‘The writer concurs with 
Pilsbry in the view that mastersi is the same species as gibba. It will appear beyond 
that the color differences specified are very secondary and are not even of varietal 
validity; furthermore, the presence or absence of a weakly developed parietal tooth 
or callus is likewise a trivial detail. 
In 1872 Pease gave the following description of a form from Guam which he 
called Partula bicolor :? 
Shell solid, perforate, acutely ovate, glossy, transversely marked with close, obsolete 
striz, straw-colored, the whorls of the spire encircled with a brownish band next to the 
suture. Peristome brownish outside and within. Whorls 4, convex, the last half the 
length of the shell. Peristome thickened, narrowly and equally expanded. Aperture 
slightly oblique, oval, with a small callus deep within on the body of the penultimate 
whorl. Length 15, diameter 9 mm.; aperture 5 mm. long, 4 mm. wide. The above may 
be distinguished from P. giéba, which occurs at the same locality, in being of smaller size, 
last whorl not inflated, and in its color. 
Pilsbry recognizes the relation of the above to Férussac’s gibba, and makes 
Pease’s form a true variety of the original species, commenting as follows: 
This form intergrades with P. gidba, and should evidently be regarded as sub-species 
of that, chiefly distinguishable by having the last whorl less swollen than in the typical 
gibba, and by having a callous nodule deep within, on the parietal wall near the columella. 
This nodule is seen very weakly developed in some examples of gibéa. Other supposed 
differences are even less constant . . . The suture may be marked with a whitish line, 
but often this is absent. No specimen I have seen has a well-developed white band along 
the suture, such as is usual in P. gibba. 
Having an extensive series of shells in hand, I find it impossible to use the 
foregoing distinctions for the separation of bicolor as a true variety. It is true that 
the coloration of Pease’s form is sufficiently distinctive to justify the establishment 
of a color-class; but the white sutural line, less swollen body-whorl, and deep 
internal nodule do not always accompany the peculiar coloration and are entirely 
independent of the latter. 
One very interesting item in the literature is a quotation given by Smith® 
in his annotations on the Hartman collection; this is an excerpt from a letter which 
Brazier wrote to Hartman under date of June 18, 1885, as follows: 
P. bicolor Pease was described from three specimens sent by me to him. They were 
picked out by me from three bushels of P. gida from Guam, collected by my late father- 
in-law, Capt. Rossiter, in a French whaler, 45 years ago. 
1 Pfeiffer, Proc. Zool. Soctety London, part 25, p. 110, 1857. 
2 W. H. Pease, Amer. Journ. Conchology, vol. 7, pp. 26, 27, plate 9, fig. 4. 
3H. H. Smith, Annals Carnegie Museum, vol. I, p. 439, 1902. 
