410 jME. a. W. ALLEN ON THE 



Some Notes on the Life-History of 3Iargaritifera panasesce. 

 By Aethub "W. Allen, B.A. (Camb.)- (Communicated 

 by Eev. T. E. E. Stebbin&, F.E.S., Sec.L.S.) 



[Read 18th January, 1906.] 



Margabitifera panases^ is a small Mother-of-Pearl Oyster, 

 of no commercial value or use. It is found in various parts of 

 the Pacific, more especially in New Gruinea waters. The species 

 was identified in 1901 as Grould's Avicula maculata by Dr. H. L. 

 Jameson, and appears in his classification of Mother-of-Pearl 

 Oysters under the above name (see Proceedings Zool. Soc. Lond., 

 April 26, 1901). 



In appearance the shell is not unlike several species of 

 Lingahs, although smaller and less convex. Its antero-posterior 

 measurement seldom exceeds 1| inches, the largest specimen I 

 have being 2| inches. In markings and colour there is much 

 variation. The ground-colour may be either white, black, dark 

 green, or purple. The shell may be either uniformly white or 

 uniformly dark. When the ground-colour is white, markings 

 generally occur as black, purple, or dark green irregularly placed 

 blotches or regular radii. The nacre, which is generally tinged 

 yellow, is transparent, except in old shells, and possesses a 

 reddish-greeu sheen. 



My observations were made consequent on the discovery of 

 an enormous natural deposition of the spat of this species in a 

 secondary lagoon of several acres in extent, which encloses one 

 of the central islands (Itamarina) of the Conflict Group Atoll, 

 British New Gruinea. During the months of February and 

 March I have estimated, on several occasions, that the deposit 

 \amounted to fifty or so young shells per square foot of suitable 

 ground. There was very little evidence of such a deposit a few 

 days alter it had been noted, and by August there was little or 

 no trace of any shells having survived. AVhat Huxley said of 

 the precaripusness of the early existence of the edible oyster is 

 equally applicable to this species: — "The minute larvse are 

 probably swallowed by everything which has a mouth large 

 enough to admit them ; and as soon as the young oysters have 

 become sedentary, they are eaten by everything which has jaws 

 strong enough to crush them." 



Many shells of this species seem to overestimate the importance 



