OXYTES. 167 



Shell geuerally of larf^c size, umbilicate or perforate, depressed, 

 in general sharply keeled, smooth, striated. 



As a rule there is no overhanging lobe to the mucous pore, though 

 one is present in 0. blanfordi and 0. pollux. Mantle : right dorsal 

 lobe triangular, well developed ; left dorsal in two parts, the 

 anterior large, the posterior very small; left shell-lohe tvitJiout 

 any tongue-liJce 'process, being merely a narrow ribbon reflected 

 over the peristome ; rigJit shell-lobe wantinrj. Generative organs : 

 hermaphrodite ducts very long, spermatheca elongate ; male organ 

 with a short spindle-shaped kale-sac and having the retractor 

 muscle attached to a large coiled caecum ; amatorial organ long, 

 well developed. 



[Although the shell-lobes are a typical chai^acter of many 

 genera of Maerochlamyina?, the coiled caecum is perhaps a more 

 important one, and more likely to be persistent. The origin of 

 shell-lobes in so many distinct genera seems due to the influence 

 of very damp atmospheric conditions in a more or less forest-clad 

 country.] 



Middle teeth of radula long, straight, without side cusps or with 

 very small representatives of them ; laterals also unicuspid or nearly 

 so. The formula in 0. cycloplax is 26 . 11 . 1 . 11 . 2Q^ in 0. orobia 

 27 . 15 . 1 . 15 . 27. 



I. Sharply Jceeled, lenticular. 



A. Openly umbilicated. 



259. Oxytes oxytes, Bs. (Helix) J. A. S. B. v, 1836, p. 351; id. 

 JL.M.X.H. (2) V, J 850, p. 215; Pfr. (Helix) Mo7i. Hel. i, 

 1848, p. 395 ; id. (Helix) iii, 1853, p. 250 ; id. (Helix) vii, 1876, 

 p. 453 ; H. Sf T. (Helix) C. I. 1876, pi. 26, fig. 1 ; Nev. Rand-l. i, 

 1878, p. 47 ; Godwin-Austen, J. A. S. B. 1880, 2, p. 158, pi. 11, 

 fig. 2 (animal) ; id. Mol. Ind. i, 1883, p. 124, pi. 30, figs. 1-3. 

 Nanina (Oxytes) fidelis, Fidton, A. M. N. H. (6) xviii, 1896, 

 p. 100. 



Shell umbilicated, depressed, obliquely striated, brownish horny, 

 sometimes with a narrow rufous band below the keel ; spire very 

 low, apex rather pointed ; whorls 5|, flattened above, the last 

 sharply keeled, slightly swollen beneath ; aperture oblique, angu- 

 larly lunate, whitish inside; peristome thin as a rule, thickened in 

 old shells, basal margin slightly arcuate and with the columellar 

 margin reflected ; umbilicus deep, exposing all the whorls. 



]\lajor diam. 45, min. 37, height 17 mm. 



llab. The ranges south of Assam, also the Dafla Hills to the 

 north. 



Some specimens are larger ; Col. Godwin-Austen has one 

 measuring 56| mm. in major diameter. 0. fidelis is a dwarf 

 variety from the Khasi Hills, measuring 31;|, 27, 12| mm. It 

 has 5 whorls and a peculiar, almost granular sculpture above and 

 below, caused by the decussation of the striation by impressed fine 

 spiral lines. 



