16 8 MR. H. F. BLANFORD'S REVIEW OF 



PART II. 



Genus MELANIA, Lamk. 

 Subgenus PHILOPOTAMIS, Layard. 



Eive species of this genus are known to me, one of which, P. regalis, Layard, is 

 doubtful, and may hereafter prove to be merely a variety of P. sulcata : of another, 

 P. decitssata, Reeve, I have only seen the three specimens in Mr. Cuming's collection, 

 and, in a genus exhibiting so much specific variation as the present, a much larger series 

 is necessary to convince me of specific distinction. The other three species are more 

 distinct from each other than is usual in the case of the allied subgenera, and differ to 

 some extent in their opercular structure, as well as in the form, &c. of their shells. Each 

 of these species is variable, and one includes several forms which have been described as 

 distinct. The following is a list of the species provisionally admitted by me : 



P. sulcata, Ueeve. P. nigricans, Reeve. 



P. regalis, Layard. P. decussata, Reeve. 



P. globulosa, Gray. 



PHILOPOTAMIS SULCATA, Reeve. (PI. XXVII. figs. 5 a-c, 11.) 



Shell ovately conic or conic, more or less strongly sulcate; sulcations regular, 

 frequently minutely decussated by transverse striae, sometimes nearly obsolete. Epidermis 

 citrine to dark brown or reddish brown, concealing the proper colouring of the shell, 

 which consists sometimes of irregular zigzags, more or less interrupted, and tending 

 towards a spiral arrangement ; more frequently of spiral bands, interrupted or continuous. 

 Spire elevated, varying in height, always eroded. Upper whorls (rarely more than three 

 remaining) variable in convexity, rounded or flattened. Last whorl globose or (rarely) 

 conoidal. Aperture gibbous to obliquely pyriform. Outer lip denticulated. Inner lip 

 thinly callous : columella flattened, arcuated, and somewhat everted, sometimes tinted 

 with In-own. Opcrculum ovately pyriform, varying in width, obsoletely spiral : nucleus 

 very near the dextral margin, somewhat variable in position. 



r l'li is species is the type of the genus. The shell is always Paludiniform, but varies in 

 globosity even in a series of specimens from the same spot. PI. XXVII. figs. 5 a & b are 

 two specimens from the same stream at Avisavella, the first being the most tumid form 

 I have seen. Pig. 5 c is a very conical form, from Hautanne, a hill in the neighbourhood 

 of Kandy. In fig. 5 a it will be seen that the sutures are deep, the upper part of the 

 whorl sloping off much less obtusely than in fig. 5 b. Other specimens in my collection 

 present intermediate gradations, so that it is impossible to regard these differences as 

 other than specific variations. The spiral sulcation, from which the species derives its 

 name, is usually fine and regular, and in some specimens is seen under the lens to be 

 regularly decussated with stria3 of growth. In other specimens these last are obsolete, 

 ifl occasionally the spiral sulcation also to a great extent, at least on the last portion of 

 the body-whorl. The upper whorls are always more or less eroded. 



The painting of the shell varies greatly. In a specimen from Avisavella the whole is 



