1921.] B. Pkashad : Sitiiiainui Moiluscs. 495 



The species was oiiginall}' described from the Malabar Coast 

 of Peninsular India, but has since been found to be widely 

 distributed in the Indian Ocean and the western parts of the 

 Pacific. 



Potamidei micropterum (Kiener), 



1866. Tympnnofonos m'cniptera. Reeve, Conch. Iconica, XV, pi. ii, sp. 



7, figs, a, h. 

 1S97. Poitimides (Tvmpn-iioton'is) microbfenis,v. Martens, op. cit., p. 



185. 

 iSgS. Ceritliiuni [Tympaiiotoiius) micropfera, Kobclt, op. cit., p. 74, 



pi. xiv, fig.s. 5. 6. 



I assign, with some doubt, a single specimen from the East 

 Coast of Sumatra to this species. The entire outer lip is broken 

 and the shape of the mouth cannot, therefore, be made out. In 

 form, .sculpture and colouration the specimen quite resembles 

 some of the authentic specimens of the species in the Indian 

 Museum collection, though the suture is a little less excavated. 



The species was hitherto known from the Phillipines and 

 Borneo. 



Subgeirus Ccrithidea, Swains. 

 Potamides obtusum (I<am.)- 



1897. Potamides (Ceritliidea) obttisiis, v. Martens, up. cit.. pp. l86, 



187, pi. i.\. fig. 22. 



1898. Cerithiiim {Ceritliidea) ohtiisuiii. Kobelt, op. cit., pp. 42, 4,^, pi. 



This species should be assigned to Lamarck and not \\'ood, as 

 Kobelt has done. The form figured and described by Quo}' and 

 Gaimard (loc. cit., pp. 126, 127, figs. 18-21) under this name is 

 not this species but P. qnadratum (Sow.') ; the shells of the two 

 are quite different and the animal also in the two species, as was 

 pointed out by Eydoux and SouleN'et,'^ has a different colouration. 

 The figure of these authors is a ver}- good representation of the 

 colouration of the animal of the true P. obtusum. 



There are a large number of specimens of this species in the 

 collection from the mangrove-swamps at Pelawan (Deli) collecte 1 

 at different times, and from the mouth of the Soengei Bataiig Kwis 

 (Serdang). Some of the Deli specimens are apparently subfossil, 

 being very much worn and rather chalky in consistency. 



This is a widely d'stributed species and von Martens has 

 given a fairly detailed list of the localities from which it has been 

 recorded. 



Potamides quadratum (Sow.). 



1897. Potamides (Ceritliidea) qiiadratiis. v. Martens, op. cit., pp. 1S7, 



188. pi. ix, fig. 23. 



1898. Cerithiiim {Ceritliidea) qyadratiim, Kobelt. op. cit.. pp. 45, 4O, 



pi. ix, fig. 8. 



1 Kobelt in his monograph {Joe. cit., p. 42) does not seem to have detected 

 this mistake, but von Martens had come to the same conclusions as myself ; his 

 figure references, however, are incorrectly cited as ig-24 instead of 18-2 1, pi. !v. 



2 Voyage ' Boitite,' Zoology, III, p. 600, pi. xxxix, figs, i, 2 (1852). 



