382 DB. H. L. JAMESON ON THE [Apr. 16, 



Colour pale greyish or greenish yellow, almost white, with 

 traces of four or five brown or green radial bands, which are 

 never very distinct. 



The inside of the lip is pale yellow, sometimes with broM n 

 markings. These, however, are less distinct than in M. siigillala, 

 and rarely if ever fuse to form the dark marginal zone character- 

 istic of that species. 



The nacre is more leaden in lustre than in M. margaritifera, but 

 slio-htly brighter than in if. sugiUata. It has a distinct yellowish- 

 green tint. The paler colour, absence of dark zone on inside of 

 lip, and different shape serve to distinguish this species from the 

 preceding. 



A better acquaintance with the geographical variation of M. 

 sugiUata may lead to M. carchariarum being regarded merely as 

 a variety of Eeeve's species. Even as such, its characters are 

 sufficiently distinct to entitle it to recogiution as a variety as 

 marked as any of those iuto which I have divided if. margariti- 

 fera. 



The name carchariarum suggested itself to me as the most 

 convenient way of associating the species with its chief locality, 

 Sharks Bay, W.A. 



Oeographical Distribution. Sharks Bay, Western Australia 

 (fished in quantities for the London markets). Sharks Bay, 

 Derby, and Kimberley (spp. sent to Mr. Martin F. Woodward by 

 Mr. B. H. Woodward, Curator, Perth Museum, W.A.). 



This shell is of small and fluctuating value as Mother-of-Pearl, 

 and yields a certain quantity of pearls in Western Australia, 

 mostly of inferior quality. At present it realizes from 10s. to 20s. 

 per cwt. in the London market, chiefly for the manufacture of 

 small buttons. 



Species 6. Margakitifeea natalensis, u. sp. (Text-fig. 93, 

 p. 383.) 



Type B.M. 1901.5.29.1; Umkomaas, near Durban, Natal. 

 Coll. J. H. Ponsonby, Esq. 



Eorm as in M. car char iarum., to which it is closely allied. 



Posterior margin of shell without, or with very faint, sinus. 

 Valves relatively fiat. The hinge is as long as the antero-posterior 

 measurement of the nacre. The postero-ventral angle of the nacre 

 is somewhat truncated, the margin of the nacre turning sharply 

 forward about halfw ay between the hinge and the ventral border. 

 The posterior angle of the hinge is a right angle. Unfortunately, 

 the lip-processes are not well preserved, but they appear to be 

 smaller and less foliaceous than in M. sugiUata and if. carcliari- 

 arum. The ground-colour is pale greenish yellow, as in the two 

 preceding species : but the radial markings are very much darker : 

 they consist of four or five broad bands of a dark purple-brown 

 colour, almost black. 



