88 ACMAEADA. 
single plume placed obliquely across the mantle cavity, laminz elongate, 
linear, partly exposed ; foot folded on itself, the sides simple, anteriorly 
thin and strap-shaped, posteriorly thick, orbicular and concave ; oper- 
culum none. Shell limpet-like ; apex sub-spiral, in the young regularly 
spiral ; interior simple ; muscular impression horse-shoe shaped. 
Genus, HIPPONYX—Blainville. 
Shell thick, obliquely conical; apex posterior ; base shelly, with a 
horse-shoe shaped impression. 
H. australis; Zam. an. s.v., vi., ~. 3353; Quoy and Gaimard, L.c., 
ili., 2. 434; pl. 72, f 25-34. Shell thick, obovate, gibbous, obliquely 
conical, reddish ; longitudinal striz thick and undulating ; apex acute, 
inflexed ; margin denticulated ; interior white, centre yellow (Lamark.) 
New Zealand and Chatham Islands. Australia. 
Animal probably yellow, with the mouth and tentacles black. 
(Quoy.) 
FAMILY—ACMAADZ. 
Radula long, with two central, and two hooked lateral teeth on each 
side in an oblique line, the inner often the larger. Head with a short 
muzzle ; mouth with cartilaginous jaws; tentacles subulate; eyes on 
bulgings at their outer bases; mantle margin simple or fringed ; gill 
forming a single pectinated plume on the side of the back of the neck ; 
foot large, ovate, with a simple impressed groove ; operculum none. 
Shell depressed, conical, or cup-shaped ; aperture wide, with a cresentic 
muscular impression, interrupted in the region of the head. 
Genus, ACMA A—Eschscholtz. 
Mantle margin fringed ; foot oval, flat. Shell patelliform, regular, 
depressedly conical, surface smooth or with radiating strize; apex anterior, 
sub-central ; aperture very wide, muscular impression non-symmetrical, the 
anterior part under the right side. 
A. pileopsis, Quoy and Gaimard, L.c., ili., p. 359, Pl. 71, f. 25-27. 
Shell ovato-convex, very finely longitudinally striated ; blackish, spotted 
or reticulated with white ; interior bluish ; margin black ; apex re-curved 
near the margin (Q. & G.) 
Length, 9 lines ; breadth, 7 lines; height, 4 lines. 
Bay of Islands and the French Pass to Dunedin. Auckland Islands. 
A. cantharus, “Reeve, Conch. Lc. (Patella,) f- 131. Shell ovate, 
rather thin, convex ; apex very anterior, sharp, hooked, smooth ; black, 
irregularly blotched with white ; interior blackish-chestnut (Reeve.) 
Differs from the last only in the larger white blotches. Tenison- 
Woods says that it comes from Tasmania. 
A. Pragcilis, Chemnitz; Quoy, 1c, i... 2: 351, p/. 71, 7:,.28:30% 
