1867.] DR. J. E. GRAY ON CATTLLtJS. f)J)7 



Fig. 2 a. Fig. 2 b. 



Fig. 2 (I. Oiitor surface. Fig. 2 h. Innei' surface. 



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



Navicella cumingiana, Recluz ; Reeve, f. 7. 



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



Hab. 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 s})ecies. Like other fluviatile shells, they are 

 liable 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 ])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, flat, thin. 



1. Paria freyceneti. 



N.freyceneti, Recluz; Reeve, Icon. t. 1. f. 4. 

 Hab. New Hebrides. 



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



2. Paria psittacea. 



N. jysittacea, Recluz; Reeve, Icon. f. 23. 

 Hab. Australian Islands. 



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

 roiv ; 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 operculum), 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, with a 



