312 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



frequently the most rugged and irregular specimens are the most 

 productive. Doubtless some of these pearls, on account of their 

 exceptional size and brilliance, must possess a very considerable 

 commercial value. The Pecten pearls are semi-transparent white, 

 covered to a great extent with a close opaque white mottling, and are 

 of various shapes and sizes. These are probably not of so much money- 

 value, as they do not exhibit the nacreous lustre of the orient pearl. 

 A magnificent pearl in Mr. Gordon Smith's possession, which he informs 

 me was found in a Pinna, is intensely black and almost perfectly 

 spherical. It is very brilliant, unique in size, weighing 55 grains, and is 

 valued at some hundreds of pounds by its possessor. 



The Mytilus pearls from Japan are beautifully lustrous, more or less 

 round, dark greenish grey or bluish black. We do not know the cause 

 of these pearls in the Ilaliotis, the Pecten, or the Mytilus from Japan. 

 The origin of them in the European mussel has been traced to the 

 presence of the larval stages of Trematode worms,' and therefore it is 

 highly probable that the Japanese pearls may have a similar origin. 

 With regard to the Haliotis and Pecten pearls we should expect their 

 occurrence to be due to the same or like causes. 



Mr. Gordon Smith informs me that the Haliotis shells are dived for 

 mostly by women, 18 Japanese fathoms of 5 feet being the limit of the 

 depth attainable by them, though doubtless the shells occur at greater 

 depths. The pearls are exceedingly rare. E. A. Smith. 



The name Bourcieria. {Read \Ath June, 1907.) — Recently, working at 

 some operculate land shells, my attention has been called to the genus 

 Bourcieria, Pfr. It was proposed by him (Zeitschr. Malak., vol. viii, 

 p. 178) in January, 1852, for B. helicina;formis, Pfr. 



Unfortunately Mons. Bourcier had already, in 1850, been honoured 

 by the genus Bourcieria, by Bonaparte in Birds — Trochilidae (see 

 C.R. Ac. Paris, vol. xxx, p. 380). 



Both names cannot stand in Zoology, and I propose to rename the 

 MoUuscan genus Pseudhelicina, taking as type the species proposed by 

 PfeifFer. E. R. Sykes. 



See Jameson, Proc. Zool. Soc, 1902, vol. i, p. 140; also Herdman, "Pearl 

 Production," Eeport Pearl Oyster Fisheries of the Gulf of Manaar, pt. v (1906). 



