296 Records of the Indian Museum. [Vol. XVI, 1919.] 



The following description of the animal (fig. 6) is based on a 

 few small spirit specimens in the collection of the Zoological Survey 

 of India, collected by Dr. A. R vS. Anderson in the year 1898 at 

 Ye-Bu, Tenasserim, Burma. 



The gills are rather broad ; the inner pair being all along 

 broader than the outer, more so in the anterior half than in the 

 posterior. The inner lamellae of the inner pair of gills are attached 

 to the abdominal sac along the anterior third only; posteriorly 

 the}- are united with one another to form an elongated diaphragm 

 extending to very nearly the margin of the mantle. The marsu- 

 pium is "formed by all the four gills, which have a sharp free 

 margin. The water-tubes are simple and the placentae elliptical. 

 The triangular palpi are not very large. The free margin of the 



mantle is entire and only slightly 

 thickened. The foot is compara- 

 tively small. The branchial opening 

 is large with well developed papillae. 

 The anal aperture, owing to the 

 absence of a mantle connection, is 

 Ts.vr-KiG. 7.— Glochidium ot yery large and extends to the point 

 '^ where the supra- anal would be ; it 

 is papillose only in the lower one-fourth of its extent. The ridge 

 of the mantle separating the branchial from the anal is very small 

 and poorly developed. 



The glochidia (fig. 7) are sub-circular, measuring "19 mm. X "iS 

 mm. 



Synoptic table for the various genera. 



A. No supra-anal aperture ... ... .. ... Pseiidodoii. 



B. A distinct supra-anal separated from the anal b\' a mantle 

 connection 



I. Marsupium formed by all the four gills. 

 • a. Gills 8-10 times as long as broad .. ... ... Baliiunitia. 



b. Gills not more than 5 times as long as broad. 



1. Inner pair of gills much broader than outer through- 

 out their length ... ... . ... Indoiiaia^. 



2. Inner pair of gills nearly as broad as the outer except 



in the anterior part ... ... .. ... Parreyssid. 



II. Marsupium formed by the outer pair of gills only, 



a. Entire length of the outer pair of gills marsupial ... Lamellideiis. 



b. Gills modified for marsupial function only near the middle 



of the outer pair ... ... ... ... P]iysnnio. 



' See also Ortmann, Nautilus, XXXI, pp. 128-131 (1918). I have been able 

 to consult all original papers by Ortmann since this paper was sent to press. 



