374 I>R. H. L. JAMESON ON THE [Apr. 16, 



variable, generally suffice to distinguish this species. _ The ground- 

 colour is pale yellowish brown, green, olive, reddish grey, dark 

 brown or black. It is characteristically marked with about 10-18 

 radial rows of white or yellow spots, running from the umbo to 

 the margin, which may be so large as to fuse and form radiating 

 bands, or may be completely suppressed. 



The interior of the lip approximates to the ground-colour o£ 

 the shell, and shows indistinct lighter markings corresponding to 

 the distal ends of the radial rows of spots. 



The nacre is highly iridescent, often somewhat steely in lustre, 

 with a marginal band of dark metallic green, bronze, or brassy 

 yellow iridescence. 



Average specimens measure 10-18 cm. in diameter, but larger 

 dimensions are at times acquired, especially by Polynesian examples, 

 which sometimes almost rival 31. inaxima in size and weight. 



Variation in this widely distributed species is so great that 

 the above specific characters \v'\\\ by no means be found to cover 

 every specimen. I find it necessary to break it up into several geo- 

 graphical races, which, although they intergrade, differ markedly 

 from one another. 



Var. a. M. margaritifet'ci ( ? typica). 



The original locality of Linna3us's type specimens in the Liiinean 

 Society's collection is not known. Linnseus gives " in utriusque 

 indice oceano " as the distribution of his Mytihis ynargaritiferus. 

 One of his specimens, a right valve, is obviously East Indian, 

 probably from the Malay Archipelago, as it agrees in all respects 

 with the " Black-edged Banda " shell of the trade. The other is 

 apparently a Bed Sea example, as it is quite indistinguishable 

 from trade samples from that locality. Linnseus's description in 

 the Mup. Beg. Ulr. is more applicable to the former than the 

 latter specimen ; so I feel inclined for the present to regard the 

 Black-edged Banda shell as representing the type of Linnseus's 

 species, and to group the geographical varieties round it. 



Australian and New Guinea shells do not show sufficient differ- 

 ences to warrant me in separating them from the type by a distinct 

 name, although their racial characters are enough to cause them 

 to be distinguished in the Mother-of-Pearl markets. 



Australian, New Gruinea, and Malayan examples are characterized 

 by dark greenish or brownish ground-colour, with well-defined 

 radial rows of white spots which do not as a rule fuse to form 

 regular striae. The margin of the nacre is usually dark green, 

 bronze, or smoky, but not so marked as in Polynesian examples. 



The form of the shell is usually that described for the species 

 generally. 



Oeographical Distribiition. Australia, all along N. coast (Aus- 

 tralian Black-lip); E. coast as far south as Moreton Bay (specimens 

 from Moreton Bay, Mus. Cuming, B.M.), W. coast to about 29° S., 

 Coasts of New Guinea and the adjacent Islands ("New Guinea 

 Black-lip "), New Britain, the Solomon Islands, &c,, and probably 

 every suitable locality in the Western Pacific. 



