42 MOLLUSCA. TRACHELIPODA. 



transversely striated ; beak ascending. 2 inches long. Inhabits 

 Indian seas. Bonan. 3, fig. 69. 



C. vertagus, Lam. Shell ventricose, with the upper half of the 

 whorls longitudinally plaited ; columella with one plait, and the 

 beak ascending ; colour yellowish white. 3 inches long. Inha- 

 bits Indian seas Bonan. 3, fig. 84. 



C. asperum, Lam. Shell turreted, acute, with longitudinal plaited 

 muricated ribs and transverse striae ; columella with one plait, 

 and the beak ascending. 2 inches long. Inhabits Indian seas. 

 Lister, pi. 1020, fig. 84. 



This shell has twelve whorls, with about the same number of longitudinal rib- 

 like plaits, on each of which are three small pointed equidistant tubercles ; the colour 

 is white, sometimes marked with three transverse narrow brown stripes on each whorl. 

 The fossil species of Cerithium are numerous. One of the most remarkable is the 

 C. giganteum, about a foot long, found at Grignon, and which is ascertained to 

 be exactly similar to a recent species from the seas of New Holland. 



SECTION II. PHYTIPHAGA. 



Without projecting syphon, and respiring generally by an ori- 

 fice ; furnished with jaws, and feeding on vegetables ; shell 

 with the aperture entire, destitute of notch or canal. 



All the species of this section of which the habits have been observed are truly 

 herbivorous. Many live on land and respire air ; others live in fresh waters, either 

 flowing or stagnant, and among these the individuals which respire air alone are un- 

 der the necessity of coming from time to time to the surface of the water, while 

 others respire through the medium of the water. A great number are marine. 

 Some families are provided with an operculum attached to the foot of the animal ; 

 while in others it is wanting. Lamarck divides this section into ten families, of 

 which the first eight, viz. Turbinacea, Scalarides, Plicacea, Macrostoma, Janthinia, 

 Neritacea, Peristomida^ and Melanides^ respire in water, and the last two, viz. Lym- 

 noeacea and Colimacea, in air. 



FAMILY I. TURBINACEA. 



Shell turreted or conoid, with the aperture rounded or oblong, 

 not widened, and the margin disunited. 



Gen. 37. TURRITELLA, Lam. Turbo, Lin. 

 Shell turreted, not nacred ; aperture rounded, entire, with the 

 margin disunited above, and the lip with a sinus ; opercu- 

 lum horny. 



All the shells of this genus are marine. They are generally furnished with strias 

 or transverse carinae, but none have vertical ribs or ridges, or spinous tubercles. The 

 margin of the aperture is disunited above and not recurved outwards. 



T. duplicata, Lam. Shell turreted, thick, ponderous, transversely 

 sulcated and carinated, whitish-yellow, with the apex red ; whorls 

 convex, with the two middle ribs prominent. 4 or 5 inches long. 

 Inhabits Indian seas. Bonan. 3. fig. 114. 



T. terebra, Lam. Shell reddish-brown, turreted, with about fifteen 

 whorls and six elevated sharp striae on each ; apex acute. 1 

 or 2 inches long. European seas. B. Erorvn, Illust. pi. 51, fig. 5 



T. exoleta, Lam. Shell whitish, turreted, with two obtuse ribs in 

 the middle of each whorl, and the whorls variegated in longitu- 



