120 NEW UNIONID^, MELANID^, ETC., 



about seven, flattened; aperture elliptical, with a slight channel, banded within; 

 umbilicus spirally carinate ; columella incurved and subangular at base. 

 Proc. Acad. Nat. Sei. 1856, p. 111. 



Hah.— Siam, S. R. House, M. D. 



Cabinet of Mr. Haines. 

 Diam. -20, Length -36 inch. 



BemarJcs. — A single specimen of this well marked Assiminea was submitted to me 

 by Mr. Haines. In form and size it resembles a species I believe described by Pr. 

 Gray, from Bengal, but difiers in being wider in the umbilicus, in being carinate, 

 in having a fine revolving line below the suture, in the number of the revolving 

 bands, and in being canaliculate. The whorls are also more flattened. There are 

 four revolving reddish-brown bands on our species, ihe lower one of which is much 

 darker, and is placed immediately outside of the spiral carina. This carina is very 

 remarkable, producing a corresponding canal within, which makes the aperture 

 slightlj' effuse at the base. There was no operculum with this specimen. Those 

 which I have of the Bengal species have the operculum exceedingly delicate, thin, 

 horny and transparent, being spiral, nearly like to those of Melania. The aperture is 

 about one-half the length of the shell. 



-"o" 



Pachtchilus PAEvrrJi. PL 22, fig. 14. 



Testa striata, obtuso-eonoidea, crassa, ferruginea; spiracurta; suturis impressis; anfraetibus senis, convexis, 

 striis transversis, exilissimis impressis ; apertura grandi, subrotunda, intus brunnea ; labro expanse, 

 valde incrassato, albo; columella alba, incrassata. 



Operculo diaphano, elliptico. 



Shell striate, obtusely conoidal, thick, rust-red; sj^ire short; sutures impressed; 

 whorls six, convex, with fine transverse impressed strise; aperture large, rounded, 

 brown within ; outer lip white, expanded, very much thickened ; columella thickened. 



Operculum translucent, elliptical. 



Proc. Acad. Nat. Sci., 1856, p. 145. 



Eab. — Siam, S. R. House, M. D. 



My cabinet and cabinet of Mr. Haines. 

 Diam. "16, Length 'oS inch. 



Remarlcs. — Three specimens of this little interesting species were submitted to me, 

 among the fresh water shells from Siam, by Mr. Haines. I recognized it at once as 

 belonging to that group of incrassate light shells which I separated from the Melaniai, 

 under the name of Pachycldlus. This little species is remarkable for its very thick 

 perimetre, the circumference being very thick and white, and the border having a 

 dark red line around it. The specimens are all covered with the oxide of iron, which, 

 when scraped off, leaves the surface of the shell whitish. The aperture is one-half 

 the length of the shell. 



