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. PI. 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 ^/a of the shell height or smaller, of a 

 semi-oval shape. In the neanic stage (figs. 40 — 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,^) is slender, nearly cylindric, with one 

 strong lamella on each wall and i 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, latet 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 inter 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 



