MOLLUSCA. _ 105 
The genus Harpa is well known, and is distinguished by 
its sharp parallel longitudinal ribs. The pillar is smooth 
and pointed at the base. 
In the genus Esurnra, the shell is smooth, and the pil- 
lar umbilicated and subcanaliculated at the base. The 
buccinum glabratum is the type of the genus. 
24. StromsBus. This Linnean genus is now converted 
into a family, distinguished by the right margin changing 
its form with age, and having towards the base an inden- 
ture or sinus. It contains four genera, strombus, rostel- 
laria, pterocera, and hippocrenis. 
In the genus Stromsus, the canal is short, the right 
margin is simple, and ends in a sinus. The S. pugilis of 
Linnzus is the type of this genus. 
In the Rosrexiiartra the canal is produced into a long 
beak, the right edge of the mouth is entire, and rests above 
on the spire, and is sometimes decurrent. The sinus is con- 
tiguous to the canal. The FR. cornuta of Mart. (Conch. iv. 
tab. 158. f. 1495,) is the type of the species. 
In the Prerocera the canal is also lengthened, but the 
right margin is dilated and digitated with a sinus near the 
base. Thestrombus pes-pelicaniof our shores is of this genus. 
25. Murex. The modern genus of this name is thus de- 
fined by Lamark: “ Testa univalvis, ovata vel oblonga ; 
basi caniculata ; suturis varicoso-tumudis, sub asperis, lon- 
gitudinalibus, et persistentibus.” In consequence of this 
restriction, the following genera, among others, have been 
instituted. 
In the genus Fascronarta, the spires are destitute of 
those longitudinal ribs which the murices always exhibit, 
while the pillar is furnished with two or three oblique folds. 
The murex tulipa of Linnzus is the type of this genus. 
