THE BONNET LIMPETS. 213 



and many-whorled, some species being smooth, others ribbed or cancellated ; aperture roundish, the 

 operculum sub-spiral. The animal has its eyes on small prominences near the outer base of the 

 tentacles, which are long and slender. The foot is pointed behind. The Rissose abound in shallow 

 water on seaweed, and live down to a depth of 100 fathoms. Seventy species have been described; 

 they are cosmopolitan in distribution. 



Genus Lithoyli/pus. This small shell has few and smooth whorls, and a large entire aperture. 

 The outer lip is sharp ; the operculum is ovate and few-whorled. It has an olive-coloured epidermis. 

 It is found living in the Danube and Central Africa in fresh water. The shell is often eroded. 

 D'Orbigny has described it from South America, under the name of Paladestrina. Seventeen species 

 have been noticed. 



Genus Truncate? la, Looping Snail. This shell is cylindrical and truncated; aperture oblong- 

 oval ; operculum very thin and somewhat spiral. The species of this genus inhabit the East and 

 West Indies, Britain, the Mediterranean, and the islands of the Corean Archipelago. The animals 

 are amphibious in their habits, being sometimes found under heaps of seaweed on the shore, and 

 sometimes in shallow water. In Corea they live gregariously, by many thousands, in the holes of 

 decayed rock and coral which border, in many places, the islands ; the spots they occupy are always 

 exposed to the spray of the sea. (Adams.) 



FAMILY XVIII. 



The "Bonnet Limpets." These shells have a more or less spiral apex, and, Limpet-like, adhere to 

 foreign bodies. The interior of the shell is simple, more divided by a shelly process, to which the 

 muscles are attached. The head of the animal is distinct, the muzzle is long, and the eyes are at 

 the outer base of the tentacles. 



" The Bonnet Limpets are found adhering to stones and shells ; most of them appear never to 

 quit the spot on which they first settle, as the margins of their shells become adapted to the surface 

 beneath, while some wear away the space beneath their foot, and others secrete a shelly base. Both 

 their form and colour depend on the situation in which they grow ; those found in the cavities of dead 

 shells are nearly flat, or even concave above, and colourless. They are presumed to feed on the 

 seaweeds growing round them, or on animalcules. A Calyptrcea which Professor Forbes kept in a 

 glass ate a small Sea Slug (Ganiodoris) which was confined with it. Both Calyptrcea and Pileopsis 

 sometimes cover and hatch their spawn in front of their foot," (S. P. Woodward.) 



Genus Galyptrcea,* " Cup and Saucer Limpet." The shell is conical, with a minute spiral 

 nucleus ; the margin is irregular ; interior provided with a half cup-shaped process, attached to the 

 apex ; outer surface of shell rough. The Cup and Saucer Limpets are found under stones in shallow 

 water, between tide-marks. Fifty species are known of almost world-wide distribution. 



Genus Crepidula, " The Slipper-shell." This shell is oval and Limpet-like ; the apex is near 

 the posterior margin ; the interior has a shelly partition covering _ its posterior half. The Crepidulse 

 are sedentary on stones and shells in shallow water, and are sometimes found adhering to one 

 another in groups of many successive generations. The specimens or species which live inside 

 empty spiral shells are veiy thin, nearly flat, and colourless. Forty species occur recent, in the 

 West Indies, Mediterranean. Cape of Good Hope, Australia, and America. 



Genus Pileopsis.^ The shell of the Bonnet Limpet is conical ; the apex is behind, and is spirally 

 curved ; the aperture is rounded ; the muscular attachment is shaped like a horseshoe. The animal 

 has a fringed margin to its mantle. P. ungarica is found on Oysters. Seven species are living in 

 Britain, Norway, the Mediterranean, East and West Indies, Australia, &c. 



Genus IIipponyx.\ The " Horseshoe-Shell " is thick, conical, oblique ; its apex is behind ; it has 

 a shelly base, bearing a horseshoe-shaped impression. Seventy species are found living in the West 

 Indies, Galapagos, the Philippines, Australia, &c. 



Genus Phorus. The shell is, like Trochus, concave beneath and irregular; the whorls are flat, 

 and more or less concealed by fragments of shell and stones ; the spire is depressed, the aperture wide, 

 the umbilicus small ; it has a thin oval operculum. " The ' Carriers ' inhabit deep water, and are 



* Latin, cali/ptra, a lady's cap. -f- Greek, pileos, a cap, and opsis, like. 



J Greek, hippos, a horse, and onyr, a hoof. Greek, phorevs, a carrier. They are also called grotto-shells. 



