FiNLAY.—New Zealand Tertiary Rissoids. 491 
differently shaped aperture. In the prominence of the basal grooves and 
almost smooth whorls it resembles N. coulthardi (Webster), but differs in 
its aperture. It is perhaps ancestral to these two Recent species. In the 
type specimen figured the basal margin is not so long and flat as in most 
specimens. 
Var. effusa n. var. | 
Differs from the species only in its aperture, which is more effuse and 
projecting below and lacks the strong angulation at junction of basal and 
outer lips. is variety makes a still nearer approach to N. coulthardi 
(Webster), but the aperture remains a little truncate below, basal lip meeting 
columella in an acute angle as in the species. 
Holotype and one paratype, from Pukeuri, in the author's collection. 
Dardanula olivacea (Hutt.). 
A rather solid, totally smooth shell, with flattish whorls. 
Localities : Castlecliff, Nukumaru. 
Dardanula rivertonensis n. sp. (Fig. 13.) 
Shell minute, elongate oval, smooth. Protoconch obtusely marked off, 
blunt, of about 2 smooth flatly-convex whorls. Whorls a 
periphery bluntly angled. Surface quite smooth. Suture rather weil 
impressed, especially in later whorls; body-whorl takes a downward curve 
near aperture, and becomes a little separated from penultimate whorl, so 
that suture becomes much deeper anteriorly. Spire conical, nearly twice 
arcuate, callous. 
Height, 2 mm. ; diameter, 1 mm. ; height of aperture, 0-7 mm. 
olotype and many paratypes, from Pourakino, Riverton (horizon 
probably near Awamoan), in the author’s collection. 
Closely related to D. olivacea (Hutt.) and D. limbata (Hutt.), but smaller 
more slender, and with the aperture more oblique (both from left to right 
and from front to back) and relatively smaller. This is the only pre- 
traces of zigzag colour-bands most prominent on the periphery, as in the 
Recent shells. 
Rissoa vana Hutt. 
This name must be omitted from Rissoid lists, as it is a synonym of 
Potamopyrgus badia Gould. The specimens clearly came not from the- 
Miocene clays at Awamoa, but from the Holocene river-gravels overlying 
the exposed parts of the beds, and, as Melanopsis, Isidora, Lymnoea, 
rium, and species of Potamopyrgus (especially P. badia) are plentiful in the 
them of numerous small land-shells is further proof of this origin; also, all 
these specimens are in a different state of preservation from the true Miocene 
