io8 Records of the Indian Museum. [Vol. XXIV, 



the young of this species and I have little doubt that Krister's 

 types also belonged to it. 



Simpson has recently described this species very fully and T 

 have nothing more to add to his description beyond noting the 

 changes that take place in the colour of the shell during growth. 

 The young shells are fulvous or chocolate-brown in the umbonal 

 region and the greater part of the shell is bordered by a broad 

 band of deep yellow on the inner side, while the dorsal slope to- 

 gether with the posterior wing and the rest of the shell are 

 shining green. As the shell grows the green and yellow gradu- 

 ally disappear and the shells as a whole become dark chestnut to 

 black ; the umbonal region, however, is always much lighter. A 

 certain amount of variation is also exhibited by the posterior 

 wing and the posterior margin ; in young shells the wing is 

 usually much broader proportionately and more marked, but as 

 the shells increase in size it becomes much narrower ; the posterior 

 margin shows much greater variation, it may be only somewhat 

 narrowed or may even take on a distinct cuneate appearance. 



In the Indian Museum collection this species is represented 

 by a large series of specimens of all ages from various localities 

 in Burma. 



Lamellidens lamellatus (Lea). 



1838. Unio lamellatus, Lea, Trans. Amer. Phil. Soc. VI, p. 19, pi. 



vi, fig. 16. 

 1889. Unio pulcher var. ponderosulus, Tappaione-Canefri, op. cit., 



PP- 35L 352. 

 1914. Lamelluiens lamellatus, Simpson, op. cit., pp. 1172, 1173. 



Both Simpson and Preston have wrongly included Idea's Unio 

 layardi in the synonymy of L. lamellatus. Lamellidens layardi 

 has no relationship whatsoever with such Burmese species as 

 L. generosus, L. lamellatus and L. scutum, but is closely allied to 

 L. marginalis. 



L. lamellatus, as has been noted above, is allied to L. genero- 

 sus, but is distinguished by its general shape, thinner shell, less 

 well developed post- dorsal wing and more delicate hinge-teeth. 



1 have examined a large series of this species from various 

 localities in Burma, in the Indian Museum collection. 



1868 

 1876 



1889 



1899 



1912 



1914 

 1915 



Lamellidens scutum (Sowerby). 



Unio scutum, Sowerby, Conch. Icon. XVI, pi. xciv, fig. 510. 

 Unio scutum, Hanley and Theobald, Conch. Ind. p. 22, pi. xlvi, 



fi ff' 1 - 

 Unio gianelli with var. degener, Tapparone-Canefri, op. cit., 



■ PP- 353- 354- 

 Unio scutum, with var. humihor, von Martens, op. cit., pp. 45, 



46. 

 Lamellidens marginalis var. sublamellata, Preston, op. cit., p. 



3°5- 



Lamellidens scutum, Simpson, op. cit., pp. 1 173, 1 174. 



Lamellidens marginalis vars. zonata {nee Hanley and Theo- 

 bald), sublamellata, scutum and humilior, Preston, op. cit., pp. 

 177, 181, fig. 19(1-3)' 



