197 
the spots. The colour inside varies. The inner border may 
be a pale heliotrope, within this an opaque white band, and 
then heliotrope as far as the muscle-scar. The interior may 
be wholly dark blotchy-brown, except the muscle-scar, which 
is white, and the front two-thirds of the spatula, which may 
be bluish-white. The brown may be more or less blotched 
about a whitish interior, or almost absent. In some a faint 
greenish-blue tint is present, deepest in the spatula. 
Diagnosis.—Its habitat, on the back of living Patella 
neglecta, Gray, suggested that it might be the young of this 
mollusc; but it is not narrowed anteriorly, the ribs are low, 
round, and approximate; the apex is less eccentric, the spots 
inside—if present—are single, and not in couples. The 
dentition and branchiz are not those of Patella, but of 
Acmaa. 
lts other ally is A. alticostata, Angas, but its ribs are 
more numerous, lower, and more approximate than in Angas’ 
species: it has not the intercostal curved concentric dark 
markings, and the internal marginal spots are disposed radially 
instead of laterally. The dentition of the radula separates 
them widely. Vide pl. xvi., figs. 3-5. 
It closely resembles the figure of Patella nigrosulcata, 
Reeve, Conch. Icon., 1885, Sp. 84a, hab. (?), and may prove 
to be this species; Patella (scutellastra) stellaformis, Reeve, 
var. migrosulcata, Reeve, Pilsbry, Man. Conch., 1891, vol. 
xiil., p. 100, pl. Ixi., figs. 66, 67. Pilsbry gives no habitat for 
this variety, but for the species he gives “Japan to Port Jack- 
son, South Australia,” etc. 
Though P. stelleformis, Reeve, is abundant, large, and 
typical in the localities where my shell is found, no inter- 
mediate forms were taken. The figures do not indicate a 
laterally concave base. If P. stelleformis has been proved 
by dissection to be a Patella, this cannot be a variety, because 
this Is an Acmaa. 
Type in my collection. 
Y Bills adcmea alticostata, Angas. 
Patella, alticostata, Angas, Proc. Zool. Soc., London, 1865, 
p. 56, pl. ii., fig. 11; Verco, Trans. Roy. Soc., 8.A., 1912, vol. 
Xxxvi., p. 183. 
Taken at Esperance Bay, 1 measuring 26 mm. long by 
22 mm. broad and 6 mm. high, in perfect condition, has only 
9 very broad, round ribs with narrow intercostal spaces, but 
is plainly of this species; at King George Sound, abundant, 
and typical up to 44 mm. by 42 mm. by 12 mm.; at Ellens- 
brook, 3, up to 20 mm.; at Yallingup, 3, up to 23 mm. ; 
at Bunbury, up to 14 mm.; at Rottnest, up to 25 mm. 
