BUG CINUM.— N ASSA .— H ARP A. 



53 



is always uncovered. The mouth is armed with a trunk, and 

 there is generally a small horny operculum. ^ 



3. The BucciNUM properly so called "-" 



{Jig. 57), has an oval, elongated shell, the 

 aperture of which is oval, nolched, and with- 

 out a canal. The operculum is complete, and 

 these animals have no veil on the head like 

 the Cerita, A great many species are known, 

 Lamarck describes fifty-eight species. 



4. We give the name of 



Nassa to mollusks that ditfer 



very little from the preceding, 



but in which the columella of 



the shell, in place of being Fig. 57. 



convex and naked, is covered by buccinum undatum. 



a plate of greater or less thickness {Jig. 58). Dolium 



also belongs to this tribe, and is 



remarkable for the length of its 



trunk and the size of its foot. 



It is without operculum, and 



the shell is recognised by being 

 almost globose, very ventricose and fur- 

 nished with projecting ribs, which follow 

 the direction of the whorls of the spire, 

 and make the margin of the aperture un- 

 dulated {fig. 59). A very large species is 

 found in the Mediterranean. 



d 



Fig. 60. — HARPA. 



59. — DOLIUM 

 GALEA. 



5. The Harps— Jfarpa — = 

 have a more oval shell, 

 furnished with projecting ribs 

 parallel with the margin of 

 the aperture, and differ from 

 the preceding in the form of 

 their foot {fig. 60). 



6. The Purpura is fur- 

 nished with an opercujum, 

 like the Buccinum properly so 



Explanation of Fig. 60. — Harp :- 

 —c. the tentacles; — d. the syphon. 



, the shell ; — 6. the foot of the animal ; 



3. What are the characters of the Buccinum properly so called ? 



4. What are the characters of the genus Nassa ? (Nassa, Latin, a net). 

 What are the charac'ers of Do'lium ? (Dolium, Latin, tub, a tun). 



5. How is the Harp characterized ? 



6. What are the characters of the genus Pc'pura ? (Purpura, Latin^ 

 purple.) 



6* 



