NERITID&. 89 
Lotta fragilis, Gray, Dief. N.Z, u., p. 240; P. unguis-alme, 
Lesson, Voy. Cogutlle, Zool., i, p. 420.  Ovate, depressed, mem- 
branaceous, pellucid, concentrically striated ; apex re-curved, marginal ; 
green, with sub-concentric brown bands; interior with a green ring 
round the muscular impression. 
Auckland to Dunedin. 
Animal uniformly clear orpiment yellow ; tentacles black (Quoy.) 
A. corticata, sf. zov. Oval, conical, with fourteen to twenty-two 
rounded, roughened ribs; apex sub-central; brownish or purplish- 
white ; interior white, sometimes with a black margin ; above the mus- 
cular impression white or brown, sometimes faintly radiately streaked 
with black. 
Height, -35 ; length, 55 ; breadth, °5. 
Dunedin. 
This small species much resembles P. pwncturata, Lamark, from 
Honduras, but it has no red marks. The animal is bluish-white, irregu- 
larly spotted with dark-purple. The shell is very variable, but easily 
recognised by its rugose ribs, looking as if it was covered with a coralline 
growth. 
DIvVISION—ASPIDOBRANCHIATA. 
Herbivorous ; upper wall of respiratory cavity not prolonged into a 
siphon ; radula with one rachis row, 4—6 intermediate, and many small 
lateral rows (rhipidoglossal.) Foot large; gills two, generally nearly 
equal ; penis none. Shell conical, spiral, or flat. These are the Scute- 
branchs of Cuvier. 
FAMILY—NERITID&. 
Lingual dentition, very similar to that of the Zyochid@, the central 
teeth few, the laterals very numerous. Head with a short broad muzzle ; 
tentacles slender and subulate, with the eyes on stout peduncles at their 
outer bases ; no head lobes or neck lappets ; foot oblong, triangular, the 
sides simple, without filaments or lateral membranes. Operculum articu- 
lated, shelly, sub-spiral. Shell depressed or oval, not umbilicated ; spire 
very short ; cavity simple, from the absorption of the interal portions of 
the whorls ; aperture semi-ovate, not pearly within. 
Genus, NERITA—Linneus. 
Animal with the mantle-margin festooned. Shell smooth or spirally 
grooved ; epidermis horny ; outer lip thickened and sometimes denticu- 
lated within ; columella with its inner edge straight and toothed. 
N. atrata, Zamark, /.c., vi., p. 603; Reeve, Conch. Ic, fi 16; 
IV. nigra, Gray, Dieff, N.Z, i., p. 240. Shell spirally striate, blue- 
black, white and chalky when eroded ; interior grey ; columella and 
near the mouth white ; mouth and outer edge of columella blue-black ; 
operculum papillose outside, pale purple, with two spiral bands of black- 
ish-purple. 
