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Show 380.] ON THE GENUS GIRASIA. 289 1. O n the Land-Molluscan Genus Girasia of Gray, with Remarks on its Anatomy and on the Form of the Capreolus of Lister (or Spermatopliore) as developed in Species of this Genus of Indian Helicidae. By Lt.-Col. H . H . G O D W T N - A U S T E N , F.Z.S., F.R.G.S., &c. [Received March 15, 1880.] (Plates XXIV.-XXVIL). In certain groups of the Mollusca the many forms run so closely one into the other that it is not easy to find differences sufficiently well marked by which to characterize even the genera. The shells (which, as a rule, have alone been described) are often very similar ; but in the animal itself, quite if not a more important part, very great diversity may be found in colour and markings, as well as in the complicated generative organs, amongst which the capreolus presents us with another specific point of difference. This is one reason for m y bringing it now more particularly to the notice of conchologists, as well as to show into what curious distinct forms it has been developed. I must state that I have not long taken up this part of the study of Malacology; and I trust that anatomists will deal leniently with any crudeness which must be inseparable from this communication. W h e n examining a large series of Helices which I had collected on the Eastern Frontier of India, I found that the body of many of them had dried up into the shell in a very perfect state. By placing these in cold water and allowing them to soak for 8 or 10 days in winter, I found that the odontophore, and in some cases even the genital organs, came out in a wonderfully perfect state of preservation. It was when examining one of these that I noticed the presence of a very hard chitinous organ (which I had never seen before) bent like a spring, from which projected at the basal end a series of long spinules : it tapered towards the posterior end, and terminated in a trumpet-shaped aperture, here also set with a few short spinules. Taking up the subject, I found that Ferd. Stoliczka had also detected and published the presence of this very peculiar chitinous organ in some species of the Indian Zonitidce, and in two very different genera as regards the shells, viz. Sesara infrendens and Macrochlamys honesta (J. A. S.B. 1871, p. 242); and had he been spared longer to science, it was his intention to thoroughly examine all the Indian species he could get, and among them some of the slug-like forms hitherto placed in the genus Helicarion, which I a m about to describe in more detail. Stoliczka suggested that the organ was one of irritation or titillation (p. 243, I. c), also that it might represent the seminal receptacle or the arrow-sac; but Professor Semper afterwards pointed out (with reference to Stoliczka's paper) that it is a spermatophore. |