176 MOLLUSCA. 
duabus biangulato quorum suprema secundum spiram volvat ; inter- 
spatio trilineato et concinne clathrato: basis convexiuscula, liris granu- 
latis concentricis ad octo insculpta ; umbilico amplo, infundibuliformt : 
apertura circularts ; columella tenut, recta, antice dentifera. 
Trochus gradatus, GouLtp; Proceed. Boston Soc. Nat. Hist., iii. 91. 
March 1849. Expedition Shells, 56. 
SHELL small, solid, ovate-conical, turreted, composed of five whorls, 
the larger of which is biangular, presenting a nearly horizontal por- 
tion next the suture, ornamented with five revolving, beaded lines, of 
which the one next the suture is largest, a vertical portion at the peri- 
phery, and a moderately convex base: the upper angle is marked by 
an elevated, rounded carina, which is continued around the middle 
of the upper whorls, to the apex : the lower angle is marked by a much 
less conspicuous carina; between the two is a central, revolving 
thread, with a much more delicate one on each side; the interspaces 
are minutely clathrate: the base is largely umbilicated; the adjacent 
portion bony-white, corrugated, and faintly subdivided by a revolving 
furrow, and circumscribed by a deep furrow, barred with lines of 
growth; between this and the periphery are seven or eight beaded 
lines, the outermost of which is largest: aperture circular; interior 
dull white; columella vertical, broad, and somewhat dentate at base, 
thin, and barely forming a septum at the umbilicus: colour cinereous, 
with about eight rusty-red, radiating flammules: tip yellow. 
Similar to 7. sulcatus, Wood, but has a more elevated spire, more 
varied colours, and a plain, rib-like carina at the angles, instead of 
spiny nodules; the columella also differs. In most respects it is like 
T. eximius, Reeve, which, however, is imperforate. 
Figure 210, profile of the shell; 210 a, base of the shell ; 210 d, 210 c, 
sculpture of the side and base, enlarged. 
Trocuus crrcumsutus (Gould ). 
Testa solida, elevata, accurate conica, imperforata: spira anfractibus 
novem subangulatis, superné declivibus, infra nodis obliquis et liris 
granosis cinctis: color cinerea, portionibus cavatis saturate olivaceis 
suturas simulantibus: basis planulata, sulcis fiiformibus concentricis 
