12 F. Stoliczka — Land-shells of Fencing Island. [No. 1, 



ed with a kind of a nacreous callose layer. The only noticeable difference 

 consists in the narrowness of the umbilicus, its width being in all the Penang 

 specimens, which I obtained, about one twelfth of the diameter of the shelly 

 while in Benson's type it is only one seventh of the same diameter. 



The species is found all over Penang hill from elevations of about 300 

 to 2500 feet, and both on the ground as well as on trees, but chiefly on the 

 latter ; it is, however, not common, and adult shells are indeed extreme 

 rarities. 



The closely allied Rh. densa, (Adams),* only differs by a slightly small- 

 er number of whorls, the last being much wider. Bh. Chevalier i, (Souleyet), 

 ditfers in the same character, though it has the umbilicus of exactly the same 

 size as the Penang variety of cymatium. 



The animal is stout and rather short, its total length being less than, 

 twice the diameter of the shell ; the posterior part of the body is the shorter 

 one, and above rather sharply ridged ; it ends with a large gland and a pro- 

 jecting horn above it. The whole body is uniform more or less dark brown, 

 laterally strongly warty and obliquely grooved ; the pedal row is very dis- 

 tinctly margined on both sides with an impressed line, and the margin of 

 the foot below it is broad, smooth, marked with alternately brown and pale 

 oblique stripes, so as to give the appearance of a variegated fringe. The 

 eye peduncles and tentacles are of usual proportionate length, dark brown 

 or even blackish, the latter with pale tips. On the whole, the general colour 

 of the specimens varies a great deal ; the young are mostly pale brown with 

 an olivaceous tinge, while in old ones the neck, including the head and 

 pedicles, become almost black. 



The mantle is somewhat paler than the body, its edge moderately 

 thickened. There are two small linguiform shell-lobes present, a right one, 

 just below the inner or posterior angle of the aperture of the shell, thus playing 

 on the inner lip, and producing its moderately distinct nacreous and callose 

 structure. The other lobe lies below the outer peripherj^ of the shell on the 

 basal side ; it projects from the outer end of a rather elongated very narrow 

 fringe, which is separated from the edge of the mantle itself The right neck- 

 lobe is entire, thick, rounded, somewhat freely projecting at the lower or umbi- 

 lical end. The left neck lobe is divided in two portions, the upper elongately 

 rounded, the lower much narrower, with the upper end somewhat pointedly 

 extended. The edge of the mantle which secretes the umbilical margin of 

 the peristome is internally considerably thickened, (comp. pi. ii, fig. 13). 



1 have not been able to see satisfactorily the exact structure of the geni- 

 tal system, but, as far as it could be examined, it appears almost entirely to 

 agree with that of Mhysota semiglohosa, figured by Semper. There certainly 

 are no appendages present — neither on the penis, nor on the seminal duct 

 or uterus. 



* E. y. Martens, Ost-Asiat. Expedit. p. 230, pi. 10, fig. 1, 



