118 LIMN^EIDJE. 



232. Planorbis merguiensis, Philippi. 



Planorbis merguiensis, Philippi tibi ? ; H. & T.,C. I. pi. 151, figs. 5, 6 ; 

 Sowerby, Conch. Icon, xx, pi. 11, sp. 85 ; Clessin, Conch.-Cab. 

 1886, p. 140, pi. 12, figs. 26-28, & pi. 20, tig. 4. 



Shell depressed, solid, striate, shining, pale horn-colour or 

 brown ; deeply umbilicate, slightly concave above ; whorls 4, 

 rapidly and regularly increasing, rounded ; suture above deep, 

 umbilical suture only lightly impressed ; the last whorl twice as 

 broad as the penultimate ; aperture broadly semilunate, oblique ; 

 labrum acute, thickened. 



Alt. 6, diam. 12 ram. 



Hob. Mergui (Coll. Duuker legit Phil.); Chybassa, Bengal 

 (var. major) (Coll. Dunker). 



Section GYRAULUS. 



yrw/MS,Agassiz,Nouv.Mem. Soc. Helv. i, 1837 (Hartmann, 1844). 

 Nautilina, Stein, Schnecken Berlin, 1850, p. 50. 



TYPE, Planorbis albus, Miiller ; Europe. 



Range. World- wide. 



Shell small, compressed, paucispiral ; whorls rapidly increasing, 

 the last broadening towards the aperture ; aperture rather wide. 



233. Planorbis (Gyraulus) compressus (Hutton). 



Planorbis (Gyraulus) compressus (Hutton), J. A. S. B. iii, p. 91 

 (no. 13), 93; Benson, J. A. S. B. v, p. 743; Martens, Mai. 

 Blatt. iv, p. 213 ; H. & T., 0. I. pi. 99, figs. 1,4; Sowerby, in 

 Reeve, Conch. Icon, xx, pi. 14, fig. 118 ; Clessin, in Conch.-Cab. 

 1886, p. 107, pi. 16, fig. 10. 



Planorbis tondanensis, Mouss., Moll. Java, p. 44, pi. 5, fig. 4. 



Shell compressed, rather broad, pale, smooth, dextral, narrowed 

 above, broad below, somewhat keeled, spire depressed ; aperture 

 obliquely pyramidal, angular above, lower margin produced. 

 (Sowerby in Reeve.) 



Alt. 3'5, diam. maj. 11*5 mm. (fig. 118 a in Conch. Icon.). 



Hob. Biver Ganges, etc. 



234. Planorbis (Gyraulus) convexiusculus (Hutton). 



Planorbis (Gyraulus) convexiusculus (Hutton), J. A. S. B. xviii, 

 pt. 2 (1849), p. 657 ; H. &. T., C. I. pi. 99, figs. 8-10 ; Sowerby, 

 in Reeve, Conch. Icon, xx, pi. 11, sp. 93 ; Clessin, Conch.-Cab. 

 1884, p. 127, pi. 17, fig. 9. 



Original description : Shell depressed, j of an inch in diameter ; 

 pale horn-colour ; polished ; closely and obliquely striate ; whorls 

 4 or 5 ; rounded ; suture well defined ; periphery subangular, but 



