MOLLUSCA FROM JUAN FERNANDEZ AND EASTER ISLAND 237 
h. 5. — Pangal, on ferns and under leaves, a few shs., max. h. 5. —_. Puerto 
Frances, about 400 m, under leaves, 6 sps., max. h. 5,5. 
Remarks: Besides the strong columellar fold and the thin parietal rib the 
aperture is sometimes armed with a small basal tooth on a transversal narrow 
callus. The columellar fold has its edge somewhat bent towards below thus 
forming a shallow furrow on its under side. Beneath it, there is a complete 
though very narrow sinus without tooth. This armature of the aperture is 
present even in small specimens of only about 4 whorls; in these the basal 
whorl is sharply angled in the periphery. In the nepionic shell (fig. 18 ¢) found 
within larger specimens, the columellar lamina is much smaller than the parietal 
one; this is reversed later on. 
Tornatellina plicosa n. sp. Pl. 9, figs. 38—42. — Shell small, turrite- 
conical, the 2—3 apical whorls a little produced, convex, the succeeding flat- 
tened or slightly convex, with shallow suture, the last obliquely angulated; 
surface polished, smooth, with oblique lines of growth, colour dark horn-brown 
or red-brown. Aperture equalling about */3 of the shell height or smaller, of a 
semi-oval shape. In the neanic stage (figs. 4o—42) several lamellae in the 
aperture: on the columella a very strong fold, issuing from its upper part, 
extending to half the breadth of the aperture and reflected downwards covering 
a strong columellar tooth filling, together with its callous base, the interior of 
the columellar sinus. Parietal wall with one strong median lamella with its edge 
reflected upwards, and sometimes outside it, about midway the space to the 
outer wall, a thin rib. Outer wall costellate within, a strong lamella projecting 
on the middle of the wall towards the space between columellar and parietal 
lamella, besides it usually further smaller ribs: on its under side I—2, and on 
its upper side usually 3 ribs, the latter sometimes alternating with thinner ones. 
Ephebic and gerontic (fig. 38) stages without lamellae on parietal and outer 
walls; sinus below columellar fold complete, without callus. Dimensions: neanic 
stage h. 2,8 up to 4, whorls 7—8 gerontic stage h. up to 5,1, whorls 9. 
Remarks: From one specimen of the ephebic stage no less than 14 well 
developed (nepionic) and 2 still younger shells were isolated by boiling in caustic 
potash. The nepionic stage (fig. 18, g) is slender, nearly cylindric, with one 
strong lamella on each wall and 1 on the columella. A small upper palatal 
rib was present in the largest individual. 
Variation: This is considerable and befalls in all stages of growth propor- 
tions and dentition of aperture; thus in all stages slender individuals occur 
together with wider ones (cf. the figures). In the neanic stage the palatal wall 
may bear from I or even none (fig. 40) to 8 (fig. 42) narrow palatal ribs besides 
the stronger palatal lamella. In the ephebic stage the palatal ribs as well as 
the lamella disappear, later on, also the parietal lamella is resorbed, and on the 
columella the dentition grows obsolete, the fold alone remaining and this also 
may be subject to reduction, though it seems as though, in the gerontic stage, 
it might increase somewhat again. To the named modes of variation may be 
added a variation of the stages zzfer se, these being of various duration; thus 
shells in the neanic stage in some cases may obtain larger dimensions and 
more whorls (fig. 39) than those which the subsequent ephebic stage possesses in 
