22 ACM^EA. 



Acmcea (f pileolus var.~) rosacea CPU., Proc. Cal. A'cad. iii, p. 213 ; 

 Amer. Journ. Conch, ii, p. 341. Collisella (7) rosacea DALL. Amer. 

 Journ. Conch, vi, p. 256. 



The shell is small, obtusely conical with an erect, subcentral apex. 

 The ground color of the surface is'u translucent white, suffused with 

 rose toward the margin, where several indistinct rays of rose color 

 appear. These are more evident on the inside. The extreme 

 nucleus is usually white. The apex is profusely dotted with minute 

 dark brown and opaque white specks of color, which are not rays, 

 nor are they often arranged with any regularity ; these are more 

 numerous on the posterior portion of the shell, but vary exceedingly, 

 from a dark reticulated brown network of lines to wavy irregular 

 penciling or sparse brown dots, usually most plenty on the inter- 

 spaces of the ribs. The surface is smooth, especially in front, but 

 from the apex radiate (especially on the posterior half of the shell) 

 a number of very marked riblets which appear as if indented from 

 below, and do not materially interrupt the smoothness of the surface, 

 though the margin is rendered slightly crenulate by them. They 

 are also of a more opaque white than the remainder of the shell, and 

 sometimes form conspicuous white rays. (Dall.) 



A. SYBARITICA Dall. PI. 9, figs. 22, 23, 24. 



Shell depressed, thin ; apex subcentral, more anterior in the 

 young. General shape rounded-oval, hardly more narrow before 

 than behind. Surface nearly smooth, with rounded concentric lines 

 of growth, in young specimens a few faint hardly noticeable elevated 

 radiating lines or riblets may be observed near the margin, which 

 is entire. Internally smooth, border polished and also the cavity 

 of the apex above the muscular impressions. Color a clear rose-pink, 

 varying from quite deep and a little livid in some specimens, espe- 

 cially the young, to a very faint pink. Apex white, even in very 

 young specimens entirely eroded, rather blunt and inconspicuous ; 

 sides of the shell ornamented with rays of a darker shade of pink, 

 more or less gathered in groups, and more or less evident, accord- 

 ing to the shade of the remainder of the shell. Internally the vis- 

 ceral area is bluish-white, usually washed with a faint yellowish- 

 brown, often hardly evident, in which case the area is whitish ; the 

 successive layers of brown sometimes appear externally around the 

 apex when eroded. The inner margin, and to some extent the 

 whole interior, exhibit the external markings or rays through the 



