GASTEROPODA. 175 
TROCHUS BICRENATUS (Gould). 
Testa pyramidata, flavescens, fiammulis rufis alternis saturatioribus 
ornata, lineis equalibus granulosis cincta: spira anfractibus septem 
ad octo, pené concavis, ad pertpheriam acutis et denticulis roseo-crenu- 
latis ad quindecim munitis: basis planulata; vortice umbilicali 
eburnea: apertura trapezotdea ; columella contorta. 
Trochus bicrenatus, Goutp; Proceed. Boston Soc. Nat. Hist., ii. 
106. April 1849. Expedition Shells, 57. 
Suett low pyramidal, acute at apex; base and height nearly the 
same ; base flat, pale yellowish, marked with delicate, equal, and equi- 
distant, beaded and revolving lines; umbilical pit, like a vortex, of a 
smooth, ivory-white polish ; whorls seven or eight, slightly excavated ; 
basal edge acute, and furnished with about fifteen scallops; above this 
are three lines of beaded granules, arranged also in oblique lines, 
which extend in the form of slight folds to the edge of the periphery, 
producing by their extension three or four crenulations of a rose-tint, 
between each of the scallops; so that the periphery, when viewed be- 
low, appears doubly crenulated ; columella sharp, contorted ; aperture 
trapezoidal ; colour flamed alternately darker and paler brown. 
Diameter seven-eighths of an inch; axis three-fifths of an inch. 
From Mr. Hawkins’s collection. 
The species most resembling it are T. fimbriatus, Lam, and T. 
Buschii, Phil.; but from these and all others it is well distinguished 
by its doubly crenate margin, as viewed from below. The profile 
outline is a little concave. It would belong to the section Polyodonta, 
of the genus. 
Figure 221, profile of the shell ; 221 a, base of the shell ; 221, 221 c, 
details of the sculpture of the side and base, enlarged. 
TRocuus GRADATUS (Gould). 
Testa parva, solida, perforata, ovato-conica, turrita, cinerea Serrugineo- 
flammulata: spira anfractibus quinque declivibus, ultimo carinis 
