^^^' •] DR. J. E. GRAY ON CATILLUS. 



f)f)7 



Fig. 2 a. Fig. 2 ^.. 



Fig. 2fr. Outer surface. Fig. 2 b. Inner surface. 



15. Catillus cumingianus. (Operculum, Fig. 2.) 



Navkella cumingiana, Re'cluz ; Reeve, f. 7, 



iV. luzonica, Schlegel ; Reeve, f. 1 1 . 



Hah. Philippines. 



The opercula of this species are very variable in shape : some are 

 much longer than broad, and have very acute lobes ; this is espe- 

 cially the case in the smaller specimens. 



There are several other species figured by Mr. Reeve that pro- 

 bably belong to this species ; but as they are destitute of opercula 

 It IS not possible to determine their true place in the system, or their 

 affinity to the other species. Like other fluviatile shells, they are 

 hable to great variations in size, form, and colour. 



2. Paria, n. g. 



Shell elliptical, mouth wide; inner lip flat, shelving upwards 

 produced and truncated in the middle, with a roundish notch on 

 each side near the margin of the cavity; operculum— shelly i)late 

 subquadrangular, lower edge straight, transverse, with a flexible flap 

 the upper edge with two lobes, the marginal lobe elongate, linear. ' 



* Shelly plate of operculum broad, fiat, thin. 



1. Paria freyceneti. 



N.freyceneti, Re'cluz; Reeve, Icon. t. 1. f. 4. 

 Hab. New Hebrides. 



** Shelly, plate of operculum narrow, high, solid, thick. 



2. Paria psittacea. 



N.psittacea, Re'cluz; Reeve, Icon. f. 23. 

 Hab. Australian Islands. 



Tribe II. Stenopomina. The operculum oblong elongate, nar- 

 row; the horny {true) operculum triangular, very oblique as 

 regards the axis of the shelly plate {occupying the triangular 

 right half of the hinder half of the entire opercidum), acute 

 near the nucleus, and rounded at the end; shelly plate of the 

 operculum elongate, thin, with two elongated ridges on the 

 upper end, the marginal one produced into a spine, loith a 



