190 MOLLUSCA. 
bilicus, but more like T. coralinus in size and general characters. Its 
uniform colour and granulation, toothed margin of the umbilicus, 
with the conspicuous tooth above, are its characters. 
Figure 224, the shell seen from above, enlarged ; 224 a, shell, with 
the animal as in motion; 2240, locomotive disk; 224 c, sculpture, 
enlarged ; 224d, aperture and umbilical region, in outline. 
Trocuus (Monoponta) tnstrictus (Gould). 
Testa parva, elevata, ovato-conica, arcté perforata, allida et maculis di- 
luté rufis prope suturam picta: spira anfractibus quinque convexius- 
culis, sub-imbricatis, sutura profunda canalformi sejunctis, hris 
acutis ubique cinctis, interspatiis concinne clathratis : basis convexa : 
apertura oblique semicircularis ; columella acuta, obliqua, in dentem 
terminante ; labro incrassato, intus sulcato, juata columellam rugoso 
et emarginato. 
Trochus (Monodonta) instrictus, GouLp ; Proceed. Boston Soc. Nat. 
Hist., 11. 107. April 1849. Expedition Shells, 59. 
SHELL small, elevated, ovate-conic, solid, white, with a series of 
about ten rufous spots near the suture ; whorls five, forming a conical 
spire, ventricose, with delicate, highly elevated rib-strie, of which 
there are about five on the upper, and ten on the last whorl : the sur- 
face of the ribs is slightly tuberculous, and the last one overhangs the 
succeeding whorl, so as to prodifce a broad, deep channel at the suture : 
the interspaces have about the same width as the ribs, and are beauti- 
fully barred with close-set lamine: base convex, with a small, deep, 
scalariform umbilicus, sculptured like the spire: aperture obliquely 
semicircular ; lip crenulated by the ribs, conspicuously sulcate within : 
columella sharp, oblique, armed with a fully-developed sharp tooth at 
base, succeeded by a deep basal notch. 
Length of the axis three-eighths of an inch; diameter three-tenths 
of an inch. 
Obtained in the Pacific Ocean. 
