Boone, Mollusca, Cruises of "Eagle" and "Ara," 1921-28 203 



Distribution : Galapagos Islands. Reef dwelling. 



Material examined : One specimen, very large, Gardner Bay, Hood 

 Island, Galapagos Islands, February 4, 1928. 



Color: Dorsally uniformly olive-black or purplish black; interior 

 surface blue-green. 



Technical description: Shell oval, or oblong-oval, moderately 

 elevated and moderately carinated, with the lateral slopes nearly 

 straight. Surface radiately ribbed. 



Measurements : 130 mm. long diameter ; 70 mm. short diameter. 



Anterior valve : Sculptured with strong radiating ribs, deep sculp- 

 tured and split toward the periphery. Twenty-four slits present. 



Intermediate valves : The central areas of these valves are sculp- 

 tured with numerous strong, small riblets, which converge forward 

 near the dorsal edge, but on the pleura they diverge strongly. The 

 lateral areas are very strong, radiately ribbed and grooved, the pos- 

 terior rib of each valve is broad and crenulated; the other ribs are 

 unequal, usually split toward the outer margin. Two or three slits 

 are present. 



Posterior valve: "With the umbo conspicuous, in front of the 

 middle. Surface sculptured with fine radiating ribs, which split 

 toward the periphery. Three slits present. 



The suture plates are broad, the sinus fairly deep and square, finely 

 toothed. 



Girdle: Formed of coarse convex scales, which are larger toward 

 the periphery. 

 References : Chiton sulcatus Wood, Gen. Conch., p. 16, fig. 1. — Sow- 



erbt, Conch. Illus., fig. 12. — Reeve, L., Conch. Icon., fig. 15. 

 Radsia sulcata Carpenter, Mss. 



Chiton (Radsia) sulcatus Tryon, Man. Conch., vol. XIV, p. 191, pi. 

 28, figs. 1, 2, 3, 4, 1892.— Stearns, Proc. U. S. Nat. Mus., vol. 16, 

 p. 404, 1893 (issued 1894).— D all, ibid, vol. 37, p. 247, 1910. 



EUPTEROPODA Boas. 

 Family: CYMBULIIDAE. 



Genus: CYMBULIA Peron and Lesueur, 1810. 

 Cymbulia peronii Blainville. 

 Type : Not located. 



Distribution : Pelagic in the Mediterranean Sea and tropical zone 

 of the Atlantic Ocean. 



