THE CINGALESE SPECIES OF PHILOPOTAMIS AND PALUDOMUS. 171 



P. nigricans has been collected by Mr. Gardner near Adams Peak, at an elevation of 

 6000 feet, by Mr. Thwaites in the Black Pool at Nuora Ellia (7000 feet), and by M. 

 Humbert* in the Paudel Oya Valley. The specimens quoted by Mr. Layard, from the 

 Balcadua Pass, do not belong to this species. Its range appears to be restricted to the 

 higher parts of the hills. 



PHILOPOTAMIS DECUSSATA, Beeve. (PL XXVII. figs. 6, 10.) 



Shell ovate-conical, smooth (or decussate ?). Epidermis citrine ; shell ornamented with 

 two broad spiral bands of colour, with a narrow interspace on the periphery. Spire rather 

 small, acute, elevately conical. Whorls 5, the upper somewhat flattened, the last large, 

 somewhat cylindrical. Aperture ovate, pointed above, equal to f ths the height of the 

 shell. Peristome white. Operculum obliquely pyriform : nucleus small, spiral, close to 

 the outer margin, subbasal. 



The only specimens I have seen of this shell are those in Mr. Cuming's collection, 

 which I take to be authentic, notwithstanding the absence of decussate sculpture ; and I 

 am unable to say how far, and in what direction, the form, &c., of the species varies. It 

 appears to be distinct, but it must be admitted that, seeing the great variability of most 

 of its congeners, it would be premature to separate it otherwise than provisionally until a 

 much larger series has been examined. PI. XXVII. figs. 6 & 10 represent one of 

 Mr. Cuming's specimens, and its operculum enlarged. 



Genus PALUDOMUS, Swainson. 



This genus, as restricted by the separation of Philopotamis and Tanalia, is character- 

 ized by the concentric structure of the adult operculum, and a spiral nucleus situated 

 about the middle of its height, and nearest to the left margin. The geographical range 

 of Paludomus is much greater than that of either Philopotamis or Tanalia, including not 

 only Ceylon, India, and Birma, but also extending in one direction to Egypt, Cape 

 Guardafui, the Mauritius, and the Seychelles, in the other to Java, Sumatra, and the 

 Island of Timor. It is remarkable, too, as contrasted with the above genera, that the 

 species have in some cases a very extensive range, following in this respect certain of the 

 low-country species of Melania, whose habit is similar, and that throughout the genus the 

 form and structure of the operculum are, so far as I have observed them, very constant. 



The species of true Paludomus enumerated from Ceylon are pretty numerous, but a 

 careful comparison of the types in Mr. Cuming's cabinet, aided by those specimens which 

 I have myself collected, or examined in Major Skinner's and Mr. F. Layard' s collections, 

 has convinced me that they are all reducible to two species, viz., 



P. cMZinoides, Beeve. 



P. Tanjoriensis^ (scil. Tanschauriensis), Gmelin. 



* These specimens are stated by Dr. Brot (Cat. d. Melaniens) to be in part smooth, in part granulated, but identical 

 in form. 



f I have taken the liberty of altering the orthography of this name to a form more in accordance with the modern 

 spelling of the place after which it is named. 



