340 



Gasteropoda. - 



-MOLLUSCA.- 



-R03TRIFERA . 



and decayed vegetable matter, preferring nearly stag- 

 nant waters, or very sluggish rivers, with a bottoru of 

 soft mud. The females of the American and European 

 species are viviparous, and the young fry are not 

 forsaken by their parent until tlie end of the second 

 month of tlieir existence. At first they are covered 

 with spiral bands of hairs, but these soon disappear. 

 Tlie genus is represented in Plate 2, tigs. 1 and 2, 

 by P. henrjalensis and P. costata. 



Tlie animals of the three following families have the 

 gill« laminar, disposed in such a way as to form an 

 oblique line across the mantle cavity, the plates or 

 laminae being elongate and linear. The shells of these 

 families are free and sub-spiral, \vith a large expanded 

 mouth ; and the animals are generally sedentary in 

 their habits, rarely, indeed, changing their place of 

 abode. 



Family— CALYPTR^ID^. 



This family is an extremely natural one both as 

 regards the shells and the animals. The animals are 

 the shell is, in external shape, like the limpet {patella); 

 destitute of an operculum (see Plate 2, tigs. 1 and 2), and 

 tlie apex being more or less spiral, and in the young shell 

 regularly so. The aperture is wide, and the interior 

 is furnished with a shelly process, variously shaped, 

 and which, as Dr. Johnston observes, is a very remark- 

 able structure. The animals of these shells carry and 

 hatch the spawn under the neck in front of the foot. 

 ']'he eggs are inclosed in a thin membranous bag in 

 small groups, and the mother " appears literally to sit 

 upon and hatch the eggs." She disposes them under 

 her belly, and preserves them, as it were imprisoned, 

 between the foot and the foreign body, to which she 

 adheres, " her patelloid shell thus serving not only 

 to cover and protect herself, but as a shield to her 

 oH'spiing. The young are developed under this kind 

 of maternal roof, and do not quit it until they have 

 strength to attach themselves to the rock, and until 

 their own shell is hard enough to afford protection 

 when so attached." — (Johnston.) The species are 

 numerous, about one hundred and ten having been 

 described, and they are world-wide in their distribution. 

 They are found adliering to stones and shells. The 

 animals of 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, whilst some 

 wear away the space beneath their foot, and others 

 secrete a shelly base. Both the form and colour of 

 tlie shells depend on the situation in which they grow. 

 Those found in the cavities of dead shells are nearly 

 Hat, or even concave above, and colourless. They are 

 presumed to feed on the sea-weed growing around 

 them, or on animalcules. — (Woodward.) The internal 

 testaceous appendage described above varies consider- 

 ably in shape, and forms a good character for separating 

 them into groups. In one tliis appendage is horizontal, 

 covering the posterior half of the elongated aperture. 

 — See Plate 2, figs. 3, 4 and 6, Crrpulula dilotata and 

 C. imguiformis. The shell is depressed horizontally, the 

 apex being sublateral and placed somewhat posteriorly. 

 Tliese form the group of Sli[iper-shells, Crf.pidulina, 



of which the genus Crepuhda is the type and chief 

 representative. Upwards of forty species have been 

 described, the greater number of which are natives 

 of South America, though several are inhabitants of 

 Australia, the West Indies, the Mediterranean, Cliina, 

 and Senegal. They are sedentary on stones and shells 

 in shallow water, and, according to M. Adanson, seem 

 to prefer those places where the sea beats with the 

 greatest violence, Tliey are often found adhering to 

 one another in groups of many successive generations. 

 Another group liave the internal testaceous appendage 

 cup-shaped, ascending obliquely, and the shell conic, sub- 

 spiral, with its apex superior, subcentral. These form 

 the group Galerina, the "Cup and Saucer Limpets. " — 

 See Plate 2, fig. 5, Cnicihidum auriculatum. In some 

 of the species of this group, as in the genus Galerus, tliis 

 shelly plate is subspiral, lateral, and adherent. One 

 of the species of this genus is British (Galerus Chi- 

 nensis), and is exceedingly diversified in colour, varying 

 from white, hyaline, and yellow, to reddish or dull 

 violet. It varies in form also, sometimes very conical 

 and smooth, at others slightly depressed, and the 

 surface covered with small, arched, elevated scales. 

 Sometimes it is smooth on one side and rough on the 

 other. Several other modifications may be observed, 

 but these must suffice. — See Plate 2, figs. 7 and 8. 



Family-CAPULID.E. 



The family of Bonnet Limpets (CaiJuUdoB) are 

 also destitute of an operculum, but the foot is folded 

 on itself, and often secretes a shelly plate or forms a 

 cavity in the body to which it is attached. — Pee Plate 

 2, figs. 1 and 2, Capnlus vnrjaricu.i. The shell is conical 

 and cup-shaped, with a sub-spiral apex (in the young 

 regularly spiral) ; and the interior is simple, without 

 any shelly appendage. The muscular impression is 

 horseshoe-shaped. The egg cases in this family 

 are membranaceous, and attached in a tuft on the 

 front of the foot. The animals are said to feed on 

 the sea-weed that grows around them. They are 

 inhabitants of nearly all the countries of the world, and 

 appear to be possessed of but limited locomotion, being 

 generally observed adhering to stones and other shells ; 

 the margins of the aperture becoming modified accord- 

 ing to the surf^ice on which they live. 



The genus Capulus has a conical, striated shell, 

 usually covered with a horny epidermis. The apex is 

 posterior and spirally recurved, and the aperture is 

 round and expanded. — See Plate 2, figs. 3 and 4, Capulus 

 ungarkus. The animal is rather sluggish and seden- 

 tary, and sometimes secretes an imperfect shelly plate 

 from its foot. In the genus Hipponyx the foot of 

 the animal secretes a truly testaceous plate, which is 

 adherent by its outer surface to living shells and other 

 marine bodies, and leaves an impression of a horseshoe- 

 shape. The shell is thick, obliquely conical, with a 

 posterior apex. — See Plate 2, figs. 9 and 1 1 , Ilipjiouyj- 

 Cornucopia;. The genus Amaltiiea is represented 

 in Plate 2, figs. 7 and 8. 



Passing by the three succeeding families, Valratidic, 

 AcieuUdce and RissoellidiF,vie come to those species 

 which have the foot round, truncated, or club-shaped. 



