114 UNIVALVES— BUCCINUM. 
The Helmets, which compose the fourth division, are 
nearly allied to the Tuns, but they may be distinguish- 
ed from them by having both of their lips (with few ex- 
ceptions) furnished with a number of strong and arti- 
culated teeth; the exterior is also covered with promi- 
nent protuberances or knobs. Among the species of 
this description may be enumerated the three follow- 
ing: B. plicatum, B. cornutum, and B.rufum, the latter 
of which is remarkable for the glowing red color of its 
mouth. 
The shells of the seventh have their exterior longitu- 
dinally ribbed, they include the species usually called 
Harps, of which the most beautiful and rare is the B. 
costatum, more frequently called the Many-ridged 
Harp. 
In the eighth division, the aperture being very wide 
and open, as in the B. monodon, B. persicum, and B. 
patulum, the species have been designated Scoops. 
The form of the B. undatum (the common English 
whelk) characterizes the tenth division ; the B. spiratum 
is remarkable for having its whorls channelled or spiral- 
ly grooved, and the B. lapillus for the durable purple 
dye which its animal produces. 
The fifteenth division contains only two species; which 
have their whorls surmounted with rows of foliations. 
The sixteenth division is more distinct than any hi- 
therto enumerated ; it comprises those shells which are 
generally known by the name of Needles; they are re= 
markable for their sharp, lengthened, and spiral form. 
