IQ3I.] B. Pkashad : Sumairan Molluscs. 499 



var. exaltata (Reciuz). 



1S511. Nen'fina exaltata, Reciuz. Jonrn. Conchyliol. [, p. 65, pi. iii. tig-. 3. 



Recluz's type-specimens of this form were collected in the 

 Negros Island. Philippines. There are a few named specimens in 

 the Indian Museum with which I have compared the Sumatran 

 specimens I assign to this varietj'. All these specimens agree fair- 

 ly with the description and figure of Reciuz. 



The Sumatran specimens were collected in the mangrove- 

 swamps at Belawan (Deli) along with those of the var. melan- 

 cstoma. 



Neritina weberi, Prashad (sp. nov.). 



(Plate xiv, figs. 15, 16). 



The shell is very thin, subcircular in outline in the ventral 

 view, regularly curved anteriorly and broadly truncated posteriorly. 

 In the lateral view it form; an arch much less than a semicircle, 

 greatly depressed anteriorly, and only slightly raised a little behind 

 the middle. The spire is very minute, lateral, recurved inwards 

 and just visible from below. The columellar plate is broad, greatly 

 inclined forwards and downwards, and with a distinct depression 

 near the margin ; the margin is entire or very slightly crenulate, 

 and is distinctly curved. ■ The dorsal surface is strongly marked 

 with concentric transverse striae. The periostracum is dark 

 olivaceous in the region of the spire, but over the rest of the shell 

 has a marked tessellated pattern formed by the crossing of dark 

 olive bars over a dark yelljwish background ; the columellar plate 

 is bluish, the shell on the inner surface is greyish but the tessel- 

 lated pattern of the outer surface is visible through the transluscent 

 shell ; the operculum is black. 



Mrasurenirnts of shells (in inillimelres) . 



M,(xiimnn diameter 



Height 



Height of aperture 



Columellar plnte 



Locality. — The two specimens of this interesting species were 

 obtained from the mouth of the Soengei Batang Kwis (Serdang) in 

 the m.mgrove-swamp region along with those of N. simoni. 



Remarks.— The species is distinguished by its very depressed 

 type of shell, its outline and the distinctly tessellated coloura- 

 tion. 



I have great pleasure in associating the name of this species 

 with that of Prof. Max Weber, who has been kind enough to send 

 me a large proportion of the collection of fresh-water and brackish- 

 water species made by him in the Dutch East Indies, and identi- 

 fied by the late Prof. E. von Martens. 



