24 
indistinct on the base. Colour pure white or white with a brown 
design in shape of a row of stripes on a white band below the 
suture, often combined with fulgurating longitudinal lines, which 
may predominate; often the brown colour markings may be con- 
fluent into 1—3 brown bands leaving a white subsutural line or 
zone; apex and base white. Spire about twice the aperture in 
height. Whorls 7, slightly convex, the last somewhat more than 
half the shell height; suture slightly impressed. Protoconch papil- 
late, of 1 1/2 smooth whorls. Aperture oblique, semiovate, sub- 
canaliculate below, angled above; 
external lip somewhat expanded 
at the middle. Columella ex- 
cavated, obliquely truncate at the 
channel. Operculum (pi. 1, fig. 
9) elongate ovate, horny, its in- 
ner margin with a small pro* 
jecting angle near the base below the claviform process, which is 
situated at the third of the operculum height. 
Locality: North Island, 11a, 1 sh., h. 4.2. — 11b, many sps., 
max. h. 6.2, br. 2.2. 
In shape and colour this species is very similar to R. zonata 
Suter and above all to R. variegata An gas, but it differs in its 
almost completely failing axial sculpture. The whole shell is pe- 
culiarly pierced by fine fissures, here and there widened to short 
lacunae appearing as opaque white maculations. This may be due 
to occasional circumstances, e. g. boring organisms. 
This species may perhaps be included in R. hanleyi of Suter. 
Having no access to authentic specimens of Sut er’s species, I 
prefer to describe and illustrate the species at hånd which differs 
from R. hanleyi Schwartz in its faint sculpture. Compared with 
R. rugulosa Hutton the present species is more siender with less 
convex whorls and less impressed suture, its aperture is less oblique. 
Some of the specimens bore egg-capsules deposited on their 
shells (one is figured). 
The radula (text-fig. 3) has the general shape of the teeth; 
the median tooth has 3—4 denticles on each side of the cusp, 
the lateral tooth 6 and the 2 marginal teeth many. 
Fig. 3. Radula of Rissoina achatina n. sp., 
half a row. X 440. 
