ig^i.j N. Annandale & R. R. S. Sewell : Vivipara. 24; 



P\RT II.— THE EDGE OF THE MANTLE AND THE 

 EXTERNAL ORNAMENTATION OF THE SHELL. 



By N. Annandale. 



In the first part of this paper Major Sewell has described the 

 structure of the free part of the mantle of Vivipara bengalensis 

 in general terms and has pointed out, as Leydig ' observed in 

 the embr\-o of V . vivipara, that the margin bears three short pro- 

 cesses corresponding in position with the three rows of minute 

 chaetae on the surface of the embryonic shell. He has further 

 noted that in the adult additional processes are both intercalated 

 between the three primary processes and produced to the left of 

 the outermost row of cliaetae in correlation with the development 

 of dark spiral bands on the shell. 



Similar facts struck me forcibly when examining two very 

 large and peculiar species of V'iviparidae in Manipur, namely L. 

 oxytropis (Benson), the shell of which is ornamented with dark and 

 prominent spiral ridges, and Lccytlwconclia Iccythis (Benson),* the 

 shell of which is almost smooth and unicolorous. 



The observations made on these species, supported as they 

 were by Major Sewell's independent observations on V. bengalensis, 

 led me to examine the edge of the mantle and the embryonic shell 

 in all species of Viviparidae in which living or properly preserved 

 material was available. The species I have examined living are 

 V. bengalensis (Lamarck), V. dissimilis (MuUer) \_ = V. remossii 

 (Benson)], V oxytropis (Benson) and L. lecythis (Benson). I have 

 also examined preserved material of the remarkable genera Mar- 

 garya, Nevill, and Taia, Annandale, in both of which the shell is 

 more highly and fantastically sculptured than in any species of 

 Vivipara. My specimens of Margarya melanoides were collected 

 in Yunnan by Mr. J. Coggin Brown, and those of Taia intha, T. 

 elitoralis, T . shanenus and T. naticoides were preserved with great 

 care by Dr. F. H. Gravely in the Southern Shan States. Some of 

 them are in excellent condition for histological stud^^ 



In addition to this Asiatic material I have been enabled by 

 the verj' kind assistance of Prof. J. H. Ashworth of Edinburgh 

 University, to examine several series of fine sections of both the 

 embryo and the adult of V. contecta (Millet), a European species 

 with a smooth, broadly banded shell. 



The material examined thus includes specimens and prepara- 

 tions of species both with smooth and with highly sculptured shells, 

 both with almost unicolorous and with conspicuously banded shells. 



l.eydig, Zeits.f. luiss. Zool. II, pi. xi, fig. 16 (1851)). 



1 



2 For the latter species I li.nve recently proposed a new genus based partly 

 on the structure of the mantle, viz. Lecythoconchn, Annandale, Rec. Ind. Miis. 

 XIX. p. 114 (1920). 



