84 HALIOTIS. 



H. GIGANTEA Chemnitz. PL 7, fig. 42. 



Shell very large, rounded-oval, quite convex, distance of apex 

 from margin between one-ninth and one-tenth the length of shell ; 

 surface with coarse, low, unequal spiral cords and broad wave-like 

 undulations ; perforations on volcano-like elevations. 



The typical form of this shell is one of the largest in the genus. 

 It is of a rounded-oval outline, the back quite convex, highest in the 

 middle. It is solid but not very thick, reddish-brown, radiately 

 streaked more or less with chocolate and green. The spiral cords 

 are low but strong, and there are irregular but very strong wave- 

 like obliquely radiating folds above. The perforations are situated 

 in high tubercles upon a strong dorsal angle, below which the left 

 side slopes steeply to the columellar margin ; this slope has low 

 spiral cords, waved or festooned below the row of holes, and it has 

 also an obtuse ridge parallel with that row, not far below it. The 

 spire is very small, quite low. Inside there are shallow spiral sulci 

 and indentations at the positions of the cords and waves of the ex- 

 terior. The nacre is light colored or silvery, to a high degree iri- 

 descent, reflections of emerald green and red predominating. The 

 muscle attachment is smooth, but its posterior and lateral outlines 

 are marked by a rugose line. Columellar plate wide, its face con- 

 cave, sloping inward. Open perforations 4. 



Length 220, width 183, convexity 50 mill. 



Japan. 



H. gigantea CHEMNITZ, Conchyl. Cab. x, p. 167, t. 1610, 1611. 

 GMELIN, in Linne, Syst. Nat. xiii, p. 3691. REEVE, Conch. Icon., 

 f. 19. LISCHKE, Moll. Jap., p. 101; ii, p. 91. SOWERBY, Thes. 

 Conch, v, t. 7, f. 44, 50. WEINKATJFF, Conch. Cab., p. 26, t. 4, f. 1, 

 2. H. tubifera LAM. An. s. Vert, vi, p. 214. H. discus REEVE, 

 Conch. Icon.,f.31 . SOWERBY, t. 5, f. 32. H. Kamtschatkana JONAS, 

 Zeitschr.f. Mai. 1845, p. 168. REEVE, Conch. Icon., f. 8. PHILIPPI, 

 Abbild. u. Beschreib. ii, t. 8, f. 12. SOWERBY, Thes. Conch, v, f. 

 33, 34. H. Sieboldii, REEVE, Conch. Icon., f. 32 a, b. H. coreanica 

 A. Ad. mss. teste Weinkauff. 



The above description is drawn from a magnificent specimen the 

 largest on record in the collection of John Ford, Esq. This typi- 

 cal form may be known by its large size, rounded outline, tubul 

 perforations, etc. The following may be considered varieties : 



