i6o Records of the Indian Musemn. [Vol. XIII, 



former group as the type and the latter as a variety, especially 

 as there is nothing in Lamarck's description to contradict this. 

 Further, Romer's figs, i to ib, pi. viii are not even typical of the 

 impudica variety in India, although they agree exactl}' with Lam- 

 arck's description. They evidently represent a pale and compara- 

 tiveh^ rare variation of the true impudica of which Reeve's figure, 

 though coarse, is a better rendering. 



The type form is particularly plentiful in the Tuticorin lagoon. 

 Out of 117 adult individuals examined therefrom, 65 belong to this 

 group, 22 to the closely related var. niorphma, while 29 belong to 

 variety impudica, one only to variety casianea and none to var. 

 aurora; while of 32 large specimens from the Tambraparni delta, 

 exactly half belonged to the type form with 8 to morphina and 8 to 

 impudica. Among 17 from the Chilka Lake, the majority (9) were 

 of the impudica variety, and only 4 out of the whole lot were of the 

 type form. The four remaining Chilka individuals consisted of 

 two var. morphina , one most typical and very beautifully ra5^ed, 

 the other obscurely rayed, and of two bridging the differences be- 

 tween varieties impudica and morphina ; both showed the typical 

 sharply defined impudica vulva, together with two well marked 

 radial bands of the morphina type. A notable feature among the 

 Chilka and Tuticorin shells is the frequency with which the impU' 

 dica va.nety shows conspicuous chevron-shaped markings, boldly 

 painte;l on the umbonar region as shown in plate vii, fig. 39. 

 Also from Arakan, Tavoy (Burma), Malacca, and Bombay. 



Of the shells from Tellicherry andTrincomalie, none belonged 

 to the type, all being variety aurora in the former case and chiefly 

 to casianea in the latter. 



(b) Variety impudica (Chemnitz). 

 (Plate V, figs. 14-18 ; plate VII, figs. 39 and 40.J 



1782. Venus meretrix seu i7npudica, Chemniti:, Conch. Cab., Vol. VI, pi. 1,7^. 

 1835. Cytheyea impudica, Lamarck, Anim. sans. Vert., 2nd ed., Vol. \'I, 



p. 299. 

 1861. ,, ,, Reeve, Conch. Icon., XIV, Cytherea, pi. iii, fig. lo. 



1915. Meretrix ovum, Preston, Rec. Ind. Mus., Vol. XI, p 300. 



1916. Meretrix ovum, .\nnandalc and Kemp, Mem. Ind. Mus., Vol. V, 



P- 350. 



This is the variety by far the most abundant on the coasts of 

 India. The periostracum is normally a pale grey colour, rarely 

 pale cream or yellow ; when removed, the shell appears porcelain 

 white, except in the postero-dorsal region where the dark coloured 

 lanceolate area, the vulva, occurs. This varies from very deep 

 blackish brown to a more frequent bluish gre\'^ of varying intensity. 

 Although albino individuals devoid of vulva and of umbonar 

 marks are sometimes met with in the Chilka Lake, normally the 

 vulva is well marked with sharply defined margin. The great 

 majority of individuals show considerable decoration of the um- 

 bones ; this most frequently takes the form of conspicuous chev- 

 ron-shaped markings either arranged in zonar manner or limited 



