192 1.] Manipur Molluscs. 609 



from Kakchitig, on the Burma-Manipur Road, and many empty 

 shells from the banks of the Amambi stream some eight miles 

 from Imphal. The shells of this species are locally known as 

 Shuni-kongrein , and are utilised for the manufacture of lime. 



LamcIIidens corrianus (lyca). 



1914. Lame! /idem corfiauiis, Simpson, op. cit., pp. 1174, II75- 



1915. Lamell ideas marginalis, subsp. corrianus, Preston, op. cit., pp. 



183, 184. 



This species is not a form of L. marginalis, as Preston thinks, 

 but quite distinct, for not only are the shells different but the 

 marsupium also is formed quite differently in the two species. 



The shell of L. corrianiis is very thin and delicate, elongate- 

 elliptical in form, with the beaks only slightly inflated and not at 

 all elevated. The dorsal slope is comparatively long and straight, 

 or nearly so, and the posterior wing is much broader than in L. 

 marginalis. There are two pseudo-cardinals (fig. 29C) in the right 

 valve, the upper of the two being rather small and thin ; in the 

 left valve also the two pseudo-cardinals are distinct, but the upper 

 and posterior one is feebly developed. The lateral teeth, vi^hich 

 are two in the left and one in the right valve, are only slightly 

 arched. 



The soft parts have already been described and figured bv 

 me as those of a form of L. marginalis. In the Manipur speci- 

 mens also the glochidia were found in the outer pair of gills only, 

 the inner pair being purelv respiratory in function. 



This is the commonest Unionid in the Manipur Valley and is 

 the only one found in the Loktak Lake. Large numbers of dead 

 shells of this species were found by the Manipur Survey party in 

 the swampy area at the north end of that body of water. Mr. .S. 

 L. Hora also collected specimens of it in various streams in the 

 vallej\ 



Genus Trapezoideus, Simpson. 



1900. Trapezoideus, Simpson, op. cit., p. 858. 

 1914. Trapezoideus, Simpson, op. cit., p. 1180. 

 1915 Trapezoideus, Preston, op. cit.. p 193. 



Simpson established this genus in 1900 for a number of rather 

 peculiar Burmese, Siamese, Cambodian and Sumatran Unionids 

 and also included in it Benson's species Unio theca from the Cane 

 River, Bundelkhand, Central India. I have not seen specimens 

 of this latter species but from the description it is doubtful 

 whether the species is congeneric with the Burmese forms.' A few 

 specimens from the Koyna Valley, Satara District, Bombay Pre- 

 sidency in the collections of the Zoological Survey, which had 

 been wrongly identified as Trapezoideus foliaceus (Gould), do not 

 belong to this genus, but are spacimens of the interesting form 



' Simpson also on p. T186 of his Catalogue {/oc. cit.) expresses a doubt as to 

 the exact systematic position of Benson's species. 



