154 CYRENID&. 
interior white, varied with red, finely radiately ribbed, those on the 
hinder margin spinulose. 
Height, -75; length, ‘87. 
Auckland to Stewart Island, 15 fathoms; rare in the south. 
FAMILY—CYRENID. 
Labial palps lanceolate. Mantle open in front, the margins simple ; 
siphons short, plain-edged, produced, either partially separated, or 
completely united to their extremities ; gills two on each side, large, 
unequal, united behind. Foot large, tongue-shaped. Shell more or 
less tumid, sub-orbicular, closed, covered with a hard, olive, brittle, 
often polished epidermis ; beaks frequently eroded; surface of valves 
concentrically striated or furrowed. Hinge composed of three, or some- 
times two diverging cardinal teeth ; lateral teeth compressed ; ligament 
external. Pallial line simple, or with a slight siphonal inflexion. Fresh 
water. 
Genus, SPHA;RIUM—Scopoli. | 
Siphons separate, diverging into two nearly equal tubes. Shell 
equivalve, thin, oblong, cordate, equilateral, more or less inflated, 
smooth or concentrically striated ; hinge with two moderately diverging 
cardinal teeth in each valve, the front of right valve, and the hinder of 
left valve smallest ; lateral teeth elongate, compressed, smooth, of right 
valve double, of left simple. 
S. novee-zelandiee, Deshayes, Cat. Conchif., Brit. Mus., p. 272, 
P.Z.S,, 1854, p. 342 ; Reeve, Conch. Ic., 7. 37. Shell ovato-transverse, 
equilateral, compressed, shining, pellucid, bluish-grey, abundantly irregu- 
larly transversely banded; anterior side obtuse, slightly declining ; 
posterior side broader, rounded, inferior margin convex; umbones 
small, obtuse, scarcely prominent; ligament small, inconspicuous ; 
hinge very narrow, bidentate ; teeth small; laterals small, the anterior 
rather larger (Deshayes.) 
New Zealand and Australia. (British Museum.) 
S. lenticula, Dunker, Mal. Blatz., viii., 1861, p. 153. : Shell, 
small, sub-orbicular, nearly equilateral, rather compressed, very thin 
pale horn-colour, or sub-straw-colour, pellucid, concentrically and deli- 
cately striated ; umbones rather obtuse. 
Length, :16 inch. (Dunker.) 
Lakes Rotoiti and Taupo. (Hochstetter.) Lake Guyon. (F. W. H.) 
This may be the same as S. denticularis, Sowerby, in Reeves’ Con- 
chologia Iconica, fig. 6, for which no locality is given. 
Genus, PISIDIUM—Pfeiffer. 
Siphons united as far.as the extremities. Shell equivalve, thin, 
usually tumid,.sub-oval, inequilateral, smooth, or concentrically striated; 
hinge with two moderately diverging teeth in each valve, the front of 
