124 



those which dwell in the sea, constituting the more numerous portion, are. 

 of a heavy solid growth, exhibiting a certain delicacy of colour and 

 marking, and are, probably carnivorous ; but those which inhabit fresh or 

 brackish water at the mouths of estuaries, or live in swamps among the 

 roots of trees, are of a lighter growth and mostly of a uniform dull brown 

 colom-, covered with a horny epidermis. These are herbivorous, and may 

 often be found suspended from the branches of trees by a mass of silken 

 threads, which the animal has the faculty of depositing as a means of attach- 

 ment. Tliis pecidiarity in the habits of CentMum Mas first observed 

 some time since in the West Indies, by the Rev. Lansdowne Guilding ; 

 it has also been described by Dr. Trail in a Natural History Journal 

 recently pubhshed at Singapore, and by Mr. Adams during liis visit to 

 Borneg in the Samarang."^ 



The shell of the Cerithia is of an elongated lanceolate form, not 

 symmetrically fluted and turbinated like Turritella, but of rather rude 

 growth, frequently presenting here and there a varix, and mostly coronated 

 with tubercles or other coarse sculpture; the cliief peculiarity in its 

 structure is the strong twisted, recurved growth of the canal. The species 

 are very numerous, and inhabit all climates within the mean temperature 

 of the Mediterranean ; in a fossil state they are stiU more abundant, and 

 afford much research for the geologist. 



The magnificent example selected for illustration is of very large size for 

 a marine species ; it is extremely rare, and I cannot learn that it has been 

 named or described. 



* The characters of the animal recited at the head of this genus are those of Lamarck, the 

 following are of more recent date, and the result of local observation : — 



The animal of Cerithium truncaimn has a broad, suborbicular, and expanded foot, and an 

 elongated, subcylindi-ical, annulated trunk of a light brown colour, with three rather broad, well- 

 defined, opaque yellow lines extending along its upper surface, the central one of which reaches 

 from the head to very near the extremity of the proboscis, where it is bifid, the two forks 

 diverging. The two lateral lines are shorter, not bifid at their extremities, and extend forward 

 on the head to within a little distance of the origin of the tentacles. The tentacles are very 

 short, annulated with the eyes, which are small, though with a distinct iris and pupil situated at 

 their tip ; whereas in all other Cerithia that have come under my observation, they are placed 

 on tubercles situated on the outer side of the base of the tentacles, or on the tentacles themselves 

 at a little distance from their origin. The foot is of a light pinky brown on its upper siu-face, 

 mottled with a deep rich brown, and on the under surface is lilac. It is found generally in 

 brackish water in Mangrove swamps, and the mouths of rivers in Singapore and Borneo. Some- 

 times they crawl on the stones and leaves in the neighbourhood, and sometimes they are found 

 suspended by glutinous threads to boughs and the roots of the ISIangroves. The operculum is 

 round, horny, with a central nucleus and concentric elements ; it is semi-tiansparent, and borne 

 upon the posterior part of the foot at its extreme end. When the animal hybei'uates, it retracts 

 itself into the shtU and brings its operculum to fit closely into the aperture, after having 

 previously affixed sixty or seventy glassy, transparent, glutinous threads to the place of attach- 

 ment, where they occupy the outer or right lip, and extend half-way around the operculum. 



There is another very handsome species, closely allied to the foregoing, which I have frequently 

 found crawling languidly on the leaves of the Fontedera and sedges iu the fluviatile marshes on 

 the banks of rivers in several parts of Borneo, and many miles iu the interior, where the water 

 is perfectly fresh, which has the eyes likewise terminal, and the proboscis marked with crimson 

 and yellow. The foot is very dark brown, and has a vivid scarlet line extending round the lower 

 margin. — Adams, Moll. Voy. Samarany. 



