PLANOKBIS. 115 



solid, polished, shining, pale yellowish horn colour ; whorls 4, 

 shouldered above, marked with rather coarse lines of growth; 

 sutures deeply impressed ; columella descending obliquely and 

 diffused above into a thick callus which joins the upper margin 

 of the peristome ; peristome simple ; aperture ovately, inversely 

 auriform. 



Alt. 8*5, diam. maj. 5-25. 



Aperture: alt. 5, diam. 3*75 mm. 



Hob. Te-ring G-ompa, 14,000 feet; Mang-tsa, 14,500 feet; 

 High Hill, Gompa, G-yantse Valley, 14,500 and Gyantse, 13,120 

 feet, in small streams. 



" Mr. Bowell informs me that the radula bears a strong re- 

 semblance to that of L. ylabra, Mull., but has fewer laterals, the 

 general appearance being more suggestive of the radula of a 

 Planorbis than that of a Limncea ; the maxilla is also very 

 remarkable, with a large blunt beak arising from the centre of 

 the semicircular piece." 



Subfamily PLANORBIIN^E. 



Shell sinistral, spire flattened or elevated. 

 Distribution. World-wide. 



Genus PLANORBIS. 



Planorbis, Geoffrey, Coq. de Paris, 1767, pp. 12, 81 ; Guettard, 



1756 (pre-Linnean\ 

 Coretus, Adamson, 1757. 

 Helix (pars), Linnaeus, 1758. 

 Angarius, Martens, 1773. 

 OrbiSj Schroter, 1776. 

 Nautilus, Lightfoot, 1786. 



TYPE of genus, P. corneus, Linn. 



Range. World- \v ide. 



Shell spiral, sometimes sinistral, spire depressed, whorls 3 to 7 ; 

 aperture semilunar, or ovate or trigonal, margin generally thin. 



227. Planorbis exustus, Desli. 



Planorbis exustus, Desli., Belang. Voy. Ind. Orient., Zool. 1834, 

 p. 417, pi. 1, figs. 11-13; ed. Lam. viii, p. 392; Midler, Synopsis 

 Test. p. 34. 



Planorbis indicm, Benson, J. A. S. B. v, 1836, p. 743 ; Marten?, 

 Mai. Blatt. xiv, p. 212 ; H. & T., C. I. pi. 39, rig. 10, & pi. 40, 

 fig. 10; Sowerby, in Reeve, Conch. Icon, xx, pi. 4, fig. 31; 

 Clessin, in Conch.-Cab. 1886, p. 43, pi. 6, figs. 20-22, & p. 116, 

 pi. 17, tigs. 1, 2. 



Original description : Testa orbiculata, utroque latere depress, 

 sutus concaviuscula ; aufractibus convexis, tenue striatis 



i2 



