I'iS MANUAL OF THE MOLLUSCA. 



They are mostly confiaed to the fresh waters of warm regions. One sp. (N. 

 flm-iatilis) is foimd in Brit, rivers, and in the brackish water of the Baltic. 

 Another extends its range into the brackish waters of the N. American rivers. 

 And the West Indian N. viridis and meleagris, are fonnd in the sea. 



'N. crepidularia has a continuous pei-istome, and approaches navicella in 

 form ; it is found in the brackish waters of India. N. corona (ISIadagascar) 

 is ornamented with a series of long tubular spines. 



Distr., 76 sp. W. Indies, Norway, Brit., Black Sea, Caspian, India, 

 Kiilippines, Pacific, W. America. 



Fossil, 20 sp. Eocene — . Brit., France. &c. 



Navicella, Lam. 



Etym., navicella, a small boat. Type, N. porceUana. PI. IX., fig. 41. 



Shell oblong, smooth, limpet-Hke ; with a posterior, sub-marginal apex ; 

 aperture as large as the shell, "nith a smaU columeUar shelf, and elongated 

 lateral muscular scars ; operculum ver}'- small, shelly. 



Distr., 18 sp. India, Mamitius, ^Moluccas, Australia, Pacific. 



FAMILY IX., TuEBiNiD^. 



Shell spiral, turbinated or pyramidal, nacreous inside ; operculum calca- 

 rious and pauci -spiral, or homy and multi-spiral. 



Animal with a short muzzle ; eyes pedunculated at the outer bases of the 

 long and slender tentacles ; head and side_s ornamented vdih. fringed lobes and 

 tentacular filaments {cirri) ; branchial plume single ; lingual ribbon long and 

 linear, chiefly contained in the visceral cavity ; median teeth broad ; laterals 

 5, denticulated; uncini very numerous (sometimes nearly 100), slender, with 

 hooked points (Fig. 15, A.). 



Marine, feeding on sea-weeds {algce). 



The shells of nearly all the turbinidee are brilliantly pearly, when the 

 epidermis and outer layer of shell ai-e removed ; many of them are used in this 

 state for ornamental pm'poses. 



TuEBO, L. Top-shell. 



Etym., turbo, a whipping-top. 



Syn., batillus, marmorostoma, caUopoma, &;c. (Gray). 



Type, T. marmoratus. PL X., fig. 2. 



Shell turbinated, solid ; whirls convex, often grooved or tuberculated ; 

 aperture large, rounded, slightly produced in front ; operculum shelly and 

 solid, callous outside, and smooth, or variously grooved and mammiUated, 

 internally horny and pauci-spiral. In T. sarmatlcus the exterior of the oper- 

 culum is botryoidal, like some of the tufaceous deposits of petrifying wells. 



Animal with pectinated head-lobes. 



