XIX. NOTES ON LAMELLIBRANCHS IN 

 T-HE INDIAN MUSEUM. 



(Plate IX.) 



By B, Prashad^ D.Sc, Assistant Superintendent , Zoological 

 Survey of India. 



I, ARCIDOPSIS FOOTEI (ThEOBAI.d). 



Theobald in 1876 ' described a peculiar species of Unionid from 

 the Gutparba Falls, Kistna River, under the name Unio footei. 

 His Latin description, drawn up from two specimens with much 

 decayed beaks, is incomplete in many respects. The existence 

 of the type-specimens is very doubtful, and Theobald's incom- 

 plete description was all that was available to Simpson * at the 

 time of the preparation of his synopsis of the Naiadae. The 

 peculiarities of shell-structure mentioned in Theobald's descrip- 

 tion led Simpson to create a new genus {Arcidopsis) for this 

 species, but he added the following qualifying foot-note :— ''' Un- 

 fortunately Theobald's Latin description is not at all complete. 

 No laterals are mentioned and he says nothing of the color of the 

 epidermis or of the nacre. The beaks were too much worn in 

 his specimens to give any characters. The shell resembles some 

 of the Areas of the Barbatia group, and may not belong to the 

 Unionidae at aU."' The concluduig remark seems to be due to 

 Theobald making a casual comparison between the shape of this 

 species and that of Area subtorta in the note following his descrip- 

 tion. Preston's^ description is merely a verbatim copy of the 

 accounts in Theobald's and Simpson's works ; he even ignored two 

 more recent memoirs that refer to this species. The first of these 

 is the incomplete monograph of Unionidae by Haas,"* in which the 

 author, besides reproducing the description and the two figures in 

 Theobald's paper, gives a full description with three figures of a 

 shell from Mysore, preserved in the Frankfurt :\Iuseum. This 

 specimen Haas assigns doubtfully to Theobald's species. It is, 

 however, clear from this description and tlie rather poor figures 

 of the hinsje, that the specimen does not belong to this species 

 but is probablv an Indonaia. The second work is an elaboration 

 by Simpson* of his "Synopsis." In this monograph he gives 



' Jotirn. As. Soc. Bengal, XV, p. 187, pi. xiv, figs. 9, cja C1S76J. 

 •^ Proc. U. S. Nat. Mas. XXII, p. 861 (1900). 

 3 Faun. Brit. Ind. Freshw. Moll., p. 196 (1915). 



* Mart, and Chemn., Conch. Cab. ed. Kiister, Die Unioniden, pp. luj-i-'i, 

 pi. xi, figs. 2-4 (1910-1914). 



^ Desc. Cat. Naiades, III, pp. 1191-1 192 ^ Michigan, 1914)- 



