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 branchiae are not those of Patella, but of 

 A cmaa . 



Its 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 pi. 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) stellceformis, Reeve, 

 var. nigrosulcata, Reeve, Pilsbry, Man. Conch., 1891, vol. 

 xiii., p. 100, pi. lxi., 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. stellceformis, 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. stellceformis has been proved 

 by dissection to be a Patella, this cannot be a variety, because 

 this is an Acmcea. 



Type in my collection. 



Acmaea alticostata, Angas. 



Patella alticostata, Angas, Proc. Zool. Soc, London, 1865, 

 p. 56, pi. ii., fig. 11; Verco, Trans. Roy. Soc, S.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. 



