128 HELCIONISCUS. 



nut-brown, becoming coppery when rubbed ; apex usually eroded 

 and coppery. 



Inside having a large, distinct central callus of pure white, a 

 lusterless whitish zone around the muscle-impression, outside of which 

 it is bright, shining, and silvery or of a pale golden tint. 



Dimensions of a moderate-sized individual : length 90, breadth 79, 

 alt. 42 mill. 



Sandwich Is. 



Patella argentata Sow^erby, in Zool. Beechey's Voy., H. M. S. 

 Blossom, Moll, p. 148, t. 39, f 7, (1839).—? Helcioniscus f argenta- 

 tus "Gray" Dall, Amer. Journ. Conch, vi, p. 278, (This may be 

 P. clypeater Less.). — Patella cuprea Reeve, Conch. Icon., f. 15, Oct., 

 1854, (See also, errata to Patella, at end of index. Conch. Icon.). — 

 Patella talcosa Gld., U. S. Expl. Exped. Moll. & Sh., p. 334, atlas 

 f. 452. — P. opea Nuttall, according to specimens deposited in Mus. 

 Acad. N. S. Phila. by Nuttall (not P. opea Eve.) 



A large, dome-shaped species, brown outside, pale-golden with a 

 white central callus inside. This species has been reported from 

 Australia, Chili and Japan, but upon wholly insufficient evidence. 



In Beechey's Voyage, the species is said to be from Chili, but as 

 the expedition also touched at Tahiti, and many of their shells be- 

 came mixed, there is no doubt of the true locality whence the types 

 were brought. The description and figure are unmistakable. 

 Several writers on the Japanese fauna have confused this with P. 

 clypeater, but this species is more raised than that, more solid, and 

 never marked with brown inside. 



H. ARTicuLATus Rccve. PI. 65, figs. 87, 88. 



Shell hexagonally ovate, attenuated in front, rather flatly de- 

 pressed, everywhere radiately ridged and striated ; olive, yellow rays 

 at the angles, ridges articulated with purple-black and white. In- 

 terior rather silvery. 



A rather compressly flattened species, divided on the surface into 

 seven to ninesubangular areas, rayed with neatly articulated ridges. 



{Rve.) 



Island of Ticao, Philippines. 



P. articulata Reeve, Conch. Icon., f. 97, 1855. 

 H. TE8TUDINARIA Linne. PL 25, figs. 16, 17, 18, 19. 



Shell large, thick and solid, oval, conic or depressed, the apex at 

 about the front third ; posterior slope convex. Surface nearly 

 smooth, but showing inconspicuous, close, low radiating riblets, gener- 



