194 PECTINIBRANCHIATA.—SCALARIADA. 
GENUS SCALARIA. 
The shell is spiral, consisting of many whorls, 
assuming a turreted form, ornamented with many 
elevated ribs, which cross the whorls in the same 
direction as the length of the shell; the aperture is 
rounded, with the lip thickened and entire. There 
is a horny operculum. 
The animal has an angularly lunate head, with 
two long pointed tentacles, and eyes immersed at 
their bases; the mouth, which opens below, has a 
retractile proboscis; the’ mantle is rudimentary ; 
the foot is triangular, grooved beneath, and fur- 
nished in front with a fold. 
In the principal section of the genus, confined to 
the warmer parts of the globe, the whorls or turns 
PRECIOUS WENTLETRAP. 
of the spire do not touch each other in any direc- 
tion: these are designated trwe Wentletraps, In 
this division is placed the shell above alluded to, 
