250 NILS HJ. ODHNER 
whorls moderately convex, suture impressed. Aperture narrowly ovate, a third 
of the total length, with one strong parietal lamella (sometimes a short acces- 
sory denticle outside it) entering about a third of a whorl inwardly; columella 
strongly twisted, convex, but without fold in adult stage; outer lip smooth 
within; in young specimens sometimes faint traces of I— 2 palatal plicae. Dimen- 
sions of the shell: height 3,8, breadth 1,5, aperture height 1,3 mm. Whorls 5 */s. 
The shell is smooth in adult, as well as in nepionic, stage, but the young 
one has, at the beginning neanic stage, very close and regular spiral striae. In 
the neanic stage, a strong columellar plate may be present or not, in the adult 
specimen it is always absent. The parietal lamella is highest near the aperture, 
and gradually lowers towards the interior. On the palatal wall some very 
feeble traces of two short spiral ribs — appearing as a faint thickening of the 
wall and not differing in colour from it — accidentally occur in young specimens; 
none are to be seen in adult ones. 
This new species evidently belongs to the group of Yornatellina perplexa, 
and forms a transition to the section ZYornatellinops of PILSBRY & COOKE Ig15, 
which lacks the columellar fold and the palatal plicae and denticles. A great 
many specimens were found in Easter Island ?/; 1917. 
From TJornatellina impressa and pusilla, which this species somewhat 
resembles, it differs by a more slender shell and a moderately convex or some- 
times flattened (never concavely impressed) outer-wall of the aperture. 
Notes on the Anatomy. Fortunately the abundant material preserved 
in alcohol made it possible to study the anatomy of this form, a matter of 
importance, since the inner organization offers the base of knowledge about 
the interrelation of the Pacific land mollusca. 
As to the external appearance, a small tongue-shaped right mantle-lobe may 
be noted, bounded by an oblique furrow running from the anus towards the back. 
The pallial organs are orthurethran: a very long kidney occupying about 
one whorl in length, and narrowing towards the front in the shape of an ureter 
debouches separately from the anus, and is furnished with a longitudinal term- 
inal fold as in Achatinellidae. The pulmonary surface is plane without visible 
veins, and hyaline white with some few black dots and maculations. 
The radula is of quite the same type as in 7ornatellina proper, thus of 
an achatinelloid structure with the teeth set in oblique rows and furnished with 
rake-like edges. A stronger entocone and a feebler mesocone are discernible 
at the edge, which bears about 8 denticles (fig. 19). No median tooth is present. 
The radula is further very thin and rugated longitudinally and it shows the 
peculiarity, also common to Zornatellina, of being annularly closed at its foremost 
end, the radula membrane forming here a circular reflexed brim. 
A thin jaw is present, consisting of an extremely thin and faint cuticular 
edge composed of some few band-like pieces which are entirely smooth and 
hyaline. The salivary glands are gray in colour, veined with fine black lines; 
they are situated close to each other chiefly on the upper side of the oeso- 
phagus, but they also surround it ventrally, and may coalesce to some extent, 
though not so intimately as in Achatinellidae (cf. PILSLRY 1915) and Torna- 
tellinidae. The oesophagus is very long and narrow, quite the same as in the 
last-named families. 
