MARINE MOLLUSCA OF THE UNITED STATES. 45 
columella simple, incurved, not tortuous; outer lip simple, acute, 
without a sinus at the forepart. Operculum annular, nucleus 
apical. Tentacles very short, with eyes at their tips. Mantle 
inclosed, with an elongated siphon. Foot small. 
1. A. DIsLocaTus, Say. Fig. 73. 
Cerithium. Journ. Philad. Acad., ii. 285. 1822. 
Terebro Petitiit. Kiener, Spec. Gen. 87, t. 18, f. 32. 
Shell small, polished, attenuated; whorls with numerous, mi- 
nute, impressed revolving lines, and fifteen to eighteen transverse 
ribs to each whorl, which are dislocated or interrupted near the 
summit of each whorl by a revolving groove as deep as the suture; 
color chocolate-brown with a pale revolving band, ribs white. 
Length 44, diam. 8 mill. 
Maryland, southward. 
2. A. CONCAVUS, Say. 
(Turritella.) Journ. Philad. Acad., v. 207. 1826. 
Shell subulate, white; volutions more than ten, concave in the 
middle, and sculptured with from two to four obsolete, impressed 
revolving lines, and with an apical and basal band of about fifteen 
longitudinal undulations on each volution; the basal band passes 
round the middle of the body-whorl; suture very slightly im- 
pressed, interrupting the continuity of the undulations in the 
adjacent bands; canal rather prominent. 
Length 13, diam. maj. 3 mill. 
South Carolina. 
Genus OLIVA, Bruguiére. 
Encyc. Meth., i. 15. 1789. 
Shell cylindrical, polished ; spire very short, suture channelled ; 
aperture long, narrow, notched in front; columella callous, stri- 
ated obliquely ; body-whorl furrowed near the base. No opercu- 
lum in the typical species. 
Animal with a very large foot, in which the shell is half im. 
mersed ; mantle-lobes large, meeting over the back of the shell, 
and giving off filaments which lie in the suture and furrow. The 
eyes are placed near the tips of the tentacles. 
About one hundred and twenty species ; subtropical. 
