104 PATELLA-SCUTELLASTRA. 



P. VIDUA Reeve. PI. (Vi, figs. 78, 79. 



Shell ovate, moderately convex ; strongly, sharply ribbed, ribs 

 alternately smaller, minutely scaled, scales distant, the alternate rib 

 sometimes nearly obsolete ; rusty-black, eroded at the apex. Inte- 

 rior whitish, with a broad rusty-black band at the edge; nucleus 

 pale rust. (Rve.) 



Island of Camiguing, Philippines. 



P. vidua Rve., Conch. Icon. f. 22, Oct. 1854. 



A moderately convex shell, rayed with sharp ribs, alternately 

 larger and smaller, each rib being roughened with minute, some- 

 what distant scales. The chief characteristic of this species lies in 

 its broad deep rust-black marginal border. (Rve.) 



(4.) Group of P. cochlear. 



Shell spoon-shaped, produced and narrowed in front ; ribs numer- 

 ous, subequal. 



P. cochlear Born. PI. 27, figs. 34, 35. 



Shell spoon-shaped, depressed, solid ; apex subcentral. Surface 

 having numerous close radiating riblets, grayish or blackish, usu- 

 ally encrusted or eroded. 



Interior white or purplish-blue, the vmscle-scar black. 



Length 60, breadth 45, alt. 15 mill. 



Cape Good Hope. 



P. cochlear Born, Mus. Ca3S. Vindob. p. 420, t. 18, f. 3. — Reeve, 

 Conch. Syst. ii, t. 136, f. 5; Conch. Icon. f. 24.— Krauss, Die 

 Siidafric. Moll. p. 48. 



The curiously narrowed anterior end gives a spoonlike appear- 

 ance to this shell. Some specimens are almost perfectly flat, and 

 have a red central callus. 



It has been made the type of a subgenus by the Adams brothers, 

 but a number of other species approach it in contour, and form con- 

 necting links Avith the oval limpets. 



(5) Group of P. lonc4icosta. 



Shell large, having some (usually 7-11) of the ribs decidedly 

 larger, rendering the outline more or less polygonal. Distribution, 

 S. Africa. 



