MOLLUSCS. 



323 



PiQ. 401. — Turbo marmoratus. 



operculum calcareous; the base of the shell is never flattened. The species are 

 mostly tropical and littoral, delighting in rocky coasts where they are exposed to the 

 force of the waves. In the Orient the larger species 

 are eaten. The largest species known is Turbo mar- 

 moratus of the Chinese Seas. In Delphinula the shell 

 is depressed, the aperture round and pearly, the um- 

 bilicus open, the operculum horny, and the whorls of 

 the shell are usually spiny. The genus is found on the 

 coral reefs of the Indo-Pacific Seas, near low-water 

 mark. Our figure shows the under surface of the shell, 

 with the body extended. 



Phasianella contains species which have somewhat 

 the shape of the genus Jiulimus among the pulmonates. 

 The shell is not pearly but is richly colored ; whence 

 the name pheasant shells. About forty species are 

 known, all from tropical seas. Those from Australian and New Zealand seas are large, 

 reaching occasionally a length of about two inches, but those from other parts of the 

 world are smaller, our West Indian forms being very small. Rotella contains a number 

 of brightly-colored depressed species from the eastern seas. In Monodotita, which is 

 much like 2hrbo in general appearance, the outer lip is much thickened and grooved, 

 while the columella is toothed. It has about the same distribution as the last species. 

 In the Malay Archipelago one of the species is eaten, notwithstanding its peppery 

 taste. 



The Neeitid^ contains thick hemispherical shells with a very small spire, a sharp 

 outer lip and a calcareous operculum which is frequently irreg- 

 ular in shape. The eyes are placed at the extremity of the 

 slender eye-stalks, which arise from the head outside the long 

 and slender tentacles. The foot is broad and triangular, the 

 apex being behind. As the animal grows, it absorbs the inner 

 part of the whorls of the shell, so that the resulting cavity is 

 simple instead of spiral. The typical genus is Nerita, which 

 has a thick or spirally grooved shell. The columella is much 

 thickened and toothed, and in one species, W. j^eloronta, this 

 columellar thickening is ornamented with a blotch of red, giving the shell the common 

 name of bleeding tooth. Most of the species are marine, but many ascend the streams 

 entering the ocean to such a distance that the water in which they live is brackish. 



Neritina is much like Nerita., but is more globular. The shells are variously orna- 

 mented with spots or bands of black and purple laid upon the polished exterior. The 

 species are mostly confined to the fresh waters of the warmer regions of the earth, 

 but some species are found in the sea. Navicella is more like the slipper limpets 

 {Crepidula) in appearance, the aperture embracing nearly the entire shell. They are 

 fresh-water forms, and the resemljlance to the limpets is strengthened by their mode 

 of life as they attach themselves by their foot to submerged stones and plants. 



The family PLEUEOTOiiAEiDiE shows resemblances to both the Trochidffi and the 

 Haliotidae. The shell is much like that found in the latter family, except that the outer 

 lip of the aperture is notched, or there is a series of perforations in the upper part of 

 the whorl. The species are largely fossil, the living forms being few in number and 

 comparatively rare. In most of the species the notch in the aperture of the shell is 



Pig. 4a2. — NeHta histrio. 



