GASTEROPODA. 
appearance of a thin columella with a deep umbilicus. P. 
dumosum is spiniferous ; P. subrectwm is simply beutt or arcuate. 
Distribution, 46 species. Silurian—Carboniferous. Europe, 
North America.’ - 
Famity 1X.—TvURBINIDzA* 
Includes PHASIANELLA (p. 263), IMPERATOR (p. 264), TURBO 
(p. 263), with the following sub-genera :— 
Callopoma, Gray, Distinguished by the extreme complexity 
of the operculum. ‘‘ The opercula of C. fluctuosum, Gray (Turbo) 
(Maz.), are flat, and covered with a dark horny layer inside, dis- 
playing about 6 whorls. Outside with a broad, central, spiral 
callus, white and granular, concealing the umbilicus, with 
extremely minute pustules over the surface, sometimes with a 
few sharp prickles. A deeply cut groove surrounds the callus, 
followed by a green, plaited, spiral frill prickly inside. Between 
this and the outer margin are 4—6 fine emerald necklaces, sup- 
ported on slender spiral ribs, with deeply channeled interspaces. 
The operculum of C. saawoswm, inhabiting Panama, is formed on 
a much coarser plan.’’—(P. Carpenter.) 
Uvanilla, Gray. Example, U. olivacea, Mexico. 
Distinguished by the absence of an umbilicus, and the bi 
_ ridged operculum. 
Distribution, 3 species. Mazatlan, Mexico. 
PHASIANELLA, 
Sub-genus, Hucosmia, P. Carpenter, 1864. 
Hiymology, eu, well, and cosmia, adorned. 
Shell solid, variegated as in Phasianella ; aperture and whor\s 
round ; axis wmbilicated. 
Distribution, 4 species. Cape St. Lucas. 
T'ROCHUS. 
With the following sub-genera and sections :— 
Margarita, Leach (p. 265). Example, T. helicinus, Fabr. 
Shell small, pearly, and umbilicated; lateral cirri, 3—7 in 
British species. No typical Z'rochi appear to inhabit North-East 
America, only those of this section. 38 species, Britain. 
Gibbula, Leach (p. 265). Example, T. magus, Linné. Shell 
low-spired and umbilicated ; lateral cirri, 3 on each side in the 
British species. 
Circulus, Jeffreys. Shell very small, nearly flat-spired, with 
an exceedingly wide and open umbilicus. Hxample, Delphinula 
* See p. 263. 
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