410 Records of the Indian Museum. [Vol. XVI, 



three to four rows of elongated papillae at its edge, while the 

 mantle covering also in this region is crenulate. The anal is 

 smooth and so is the margin of the mantle below the branchial. 



The glochidia (fig. 4) are very like those of Physunio ferrugi- 



neus ' in outline, but have the hooks 

 much better developed. They mea- 

 sure "23 mm. X *I9 mm. 



The animal of this sub-genus 

 differs from that of Unio, s.s., as 

 Text-fig. 4.-Glochidium of f7»,-o described by Ortmann,^ in having 

 {Rho}nbitnio)sem{rHgattis, X 75. the whole organism of a much 



more compact type, the gills much 

 shorter and broader, in the different shape of the palpi, the extent 

 of the marsupial region and the very different shape of the glochi- 

 dium. 



Eolymnium, sub-gen. nov. 



This new sub-genus is proposed for the species Unio terminalis ' 

 Bourguignat, and its allies. A large number of specimens of this 

 species were collected by Dr. Annandale from the Lake of Tiberias 

 in October, 1912. 



Simpson {loc. cit., p. 689) includes this species in his group of 

 Unio pictorum (Linn.), the type of the section Lymnium, and Ger- 

 main has followed him in calling the species Unio {Lymnium) termi- 

 nalis. The soft parts of Unio terminalis ^ however, are very different 

 from those of U. pictorum as described by Ortmann {loc. ci7., pp. 274- 

 275). I have, therefore, found it necessary to separate U. terminalis 

 into a distinct sub-genus. Reference here might also be made to 

 the interesting controversy^ started by Thiele ^ regarding the validity 

 of the generic name Unio. Haas * took objection to his statement 

 and expressed the opinion that the name Unio could not be re- 

 placed by Lymnium, because Bruguiere's name had priority over 

 that of Oken. Ortmann,^ who has recently summed up the whole 

 situation very well, has come to the conclusion that Lymnium is 

 nothing more than a synonym of Unio as restricted by Bruguiere. 



The animal (fig. 5) of the sub-genus Eolymnium may be des- 

 cribed as follows : — The gills are elongate but relatively shorter than 

 in Unio pictorum. The inner pair of gills is much broader than the 

 outer throughout their length and the free region of the inner lamellae 

 of the inner pair of gills is also much larger than in U. pictorum ; the 

 other attachments of the gills are similar to those described for Rhom- 

 bunio. The outer pair of gills, except at the extreme anterior end, 

 is marsupial, as was ascertained by cutting sections. The palpi are 

 similar to those of U. pictorum except that they are more pointed 



i Rec. Ind. Mils., XIV, p. 184, pi. xxii, fig. 10 (1918). 

 ■^ Ann. Carnegie Mus., VIII, pp. 273-275 (1911-12). 

 3 Nachr. Bl. deutsch. Malakozool., XLII, p. 29 (1909). 

 * Ibid. pp. 68-72 (1909). 

 6 Nautilus, XXV, pp. 88-91 (191 1). 



