248 PEOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



the present of tlieir anatomy, and what value it may be in future 

 classification. 



The classification of the Indian Land MoUusca having up to the 

 present been based mainly on such conchological knowledge we 

 possessed, aided by a few external characters of the animals, I have 

 thought it might be of interest, and particularly to the members of 

 this Society, to treat the subject from a malacological point of view. 

 I propose to limit my observations to this large, interesting, and, 

 I believe, very ancient family, the Zonitidae. Semper, Yon Martens, 

 Stoliczka, Simroth, and others have done much excellent pre- 

 liminary work on the anatomy and external form of the animal in many 

 of the genera described by them, and these authorities I shall quote. 

 The material I have myself obtained, examined, and refer to, may 

 perhaps interest other workers, and, if it does nothing more, will, 

 I trust, extend the knowledge of present distribution, and give 

 perhaps a glimpse of the past history, or phylogeny of some genera 

 and subgenera, 



A study of this family extending over many years enables me to 

 show to what extent variation in the internal organs has proceeded 

 in different species, and how restricted such differences are to species 

 within certain well-defined areas. This variation seems to play 

 round certain organs, leaving others unchanged. 



In this investigation I have taken cognizance of every character, 

 internal or external, that I found to vary, and it naturally follows 

 that some organs assume a greater prominence than others. I have 

 disregarded the nervous system, for it is a study in itself. Although 

 in the more slug-like fonus there may be found considerable modi- 

 fication of the salivary glands, the form of the buccal mass, the coils 

 of the intestine, and the position of retractor muscle attachments, 

 they may well be also treated as specific differences, and at present 

 left alone ; nor does the form of the mucous pore assist very much. 

 The value of the arrangement of the intestinal coils in classification 

 has lately been very well exemplified by H. A. Pilsbry and 

 E. C. Vanatta in a paper on a " Eevision of North American Slugs," ^ 

 as well as in a paper on the " Phylogeny of the Genera of Arionidse." ^ 



I must here quote a paragraph from the above joint paper :^ 

 " Trivial and unsatisfactory as are the external features of slugs, 

 the details of their internal morphology are wonderfully varied. 

 Everywhere there are important characters, and those who starve 

 their souls on a mere study of the genitalia and oral armature miss 

 the best part of the feast." This is true of every family, but it 

 applies more particularly to the Zonitidse. Valuable material is con- 

 stantly coming into the country, yet how much of it, only partially 

 examined, is thrown away. The animal is mutilated, the head being 

 severed from the body, and the most interesting organs destroyed 



» Proc. Acad. Nat. Sci. Philadelphia, 1898, pp. 219-261. 

 - Ante, p. 94. 

 ■^ T.c, p. 219. 



