PHILALAXKA. 2^ 



tennis, pallide cornea, striatula ; spira conoidea, apice obtusa, 

 sutura impressa. Anfr. 6 angusti, convex!, ultimus baud clescen- 

 dens, subtus rotundatus. Apertura subverticalis, rotundato 

 lunaris ; peristoma simplex, marginibus distantibus, coiumellari 

 reflexiusculo. 



" Diam. maj. 2, min. 2|, alt. If mm." (Blanford.) 

 Hob. India: Nilgiri Hills, Pykara and Neddiwuttom. 



40. PMlalanka thwaitesi, Pfeiffer. 



Helix thwaitesi, Pfeiffer, P. Z. S. 1853, p. 125; Reeve, Conch. Icon. 



vii, 1854, pi. 191, fig. 1336; Hanley & Theobald, Conch. Ind. 



1875, pi. 128, figs. 7-10. 

 Helix (Microcystis) thivaitesi, Pfeiffer, Malak. Blatt. ii, 1856, 



p. 123. 

 Nanina (Microci/stis) thicaitesi, Try on, Man. Conch, ser. 2, ii, 1886, 



p. 118, pi. 39,' fig. 5. 

 Microcystis nuwara, Jousseaume, Mem. Soc. Zool. France, vii, 1894, 



p. 273. 

 Philalanka thivaitesi, Godwin-Austen, Moll. India, ii, 1907, p. 19.), 



pi. 112, fig. 1 (jaw & radula). 



Original description : " T. aperte perforate, convexo-depressa, 

 si riatula nitida, cereo-hyalina ; spira breviter conoidea, obtusula ; 

 sutura profunda, submargiiiata ; anfr. 6| convexi, arete convoluti, 

 ultimus non desceudens, basi inflatus; apertura verticalis, lunaris ; 

 perist. rectum, acutum, margine coiumellari arcuatim oblique 

 d^scendente, ad perforation em vix dilatato. 



" Diam. maj. 5, min. 4j, alt. 3 mill." (Pfeiffer.) 



Hob. Ceylon (Thtvaites) ; Nuwara-Eliya (Simon) ; Ambagaum\va 

 (Collett). 



Under a strong lens the shell is seen to be densely covered with 

 spiral striae. Mr. E. E. Sykes established the fact (Proc. Malac. 

 Soc. London, iii, 1898, p. 65) that Microcystis nuwara, Jousseaume, 

 and the present species are identical. Jousseaume, in fact, based 

 his species upon the figure of thwaitesi in Conch. Icon., which 

 was drawn from Pt'eiffer's type. 



Lt.-Col. Godwin-Austen investigated the anatomy and describes 

 the genitalia, but he gives no figures. 



Var. suavis, Jousseaume. 



Microcystis suavis, Jousseaume. Mem. Soc. Zool. France, vii, 1894, 

 p. 273, pi. 4, fig. 3 ; Collett, J. A. S. B. Ceylon Branch, xv, 1897 

 (1898), p. 12. 



Microcystis thwaitesi, var. suavis, Sykes, Proc. Malac. Soc. London, 

 iii, 1898, p. 65. 



Differs from the typical form in having a slightly more depressed 

 spire, a somewhat larger umbilicus, and in the mouth being some- 

 what different in shape. 



Hob. Ceylon : Nuwara Eliya (Simon); Ambagamuwa (Collett). 



