OXYTES. 167 



Shell generally of large 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-lobe without 

 any tongue-like process, being merely a narrow ribbon reflected 

 over the peristome ; right sliell-lobe wanting. 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 ccecum ; amatorial organ long, 

 well developed. 



[Although the shell-lobes are a typical character of many 

 genera of Macrochlamyinse, 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 . 26, in 0. orobia 

 27 . 15 . 1 . 15 . 27. 



I. Sharply Iceeled, lenticular. 

 A. Openly umbilicated. 



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

 A.M.N.H. (2) v, 1850, p. 215; Pfr. (Helix) Man. Hel. i, 

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

 p. 453 ; H. 8f T. (Helix) C. I. 1876, pi. 26, fig. 1 ; Nev. Hand-l. i, 

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

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

 Nanina (Oxytes) fidelis, Fulton, 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 j, 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. 



Major diam. 45, min. 37, height 17 mm. 



Bab. 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 31J, 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. 



