AAW) Bulletin American Museum of Natural History [Vol. LIII 
form two smooth, thin and very prominent keels on the last two to five 
whorls, the upper keel being usually the more prominent. The base has 
numerous (usually 10 to 16) smooth spiral cords, as in the form granulosa 
(Pl. X XU, tes. 3-30; Pl. XXIV, fies. 11g). 
The neanic stage of fusca seems to be always of the rather coarse- 
ribbed granular type. : 
III. In another form, which has been called mutans Gould,! the 
upper and, to a smaller extent, the fifth spirals are more or less extended 
to form carine, as in form fusca; but they diminish again, leaving the 
last whorl simply granose-costate, as in form granulosa (Pl. XXIV, 
figs. 2, 4). 
This form, which appears to be a blend between granulosa and 
fusca, is extremely rare. No two examples are alike. The ribbing varies 
from coarse to rather fine. The carine may exceptionally become as 
strong as in fusca, but generally are much less developed, with the crest 
lobed at intersections with the ribs. 
Banana. (Pl. XXIV, figs. 1-4). The specimens here are large. 
Length, 41.5 mm.; diameter, 27.6 mm.; 7 whorls; form fusca. 
66 34.5 a 18.5 246 a 66 66 
oo AGO) K 16.0 d “granulosa. 
a 30.0 66 £75 9 a a a 
In this very large series the forms granulosa and fusca are repre- 
sented by an equal number of individuals. The form mutans, however, is 
much rarer, as shown by the following figures: 
Number of 
) individuals 
POEM ROM INOS ta Pon uci rome Mie ek uy eye gee gue aso a i 18 
NRC OL da een ee ote en. ay, Taare EME Meare ee tate ec 1927 . 
TT ELON a emtrk Ore US a RMen te arr aneUnTEM Mit: See tere termie Sere 167 
MOU er epocmemay | Meera sie bed MAN WRT Mies eee. ea 253 
MER et NR otc, mse ani aia. lta TRUS | ign) ure 4245 
Malela. (PI. XXIII, figs. 3-3h). The form granulosa reaches about as 
great a size as at Banana, and shows similar coarser and finer ribbed 
forms. 
Form fusca is constantly smaller than those of Banana, and often 
more slender. 
Length, 34.5 mm.; diameter, 13.0 mm.; 6 whorls. 
TEs cen tein ss aes Ce 
t : ‘ gee f 
The name is used as restricted by Reeve. Gould’s description covered various other forms also. 
