77 . 
S.A. NAT., VOL. XV. 
June 12th, 1934. By Bernard C. Cotton and F. K. Godfrey. 
SOU1 H AUSTRALIAN SHELLS. 
(hidtiding descriptions of Xew Genera and Species). 
(By Bernard C. Cotton Sc F. K. Godfrey). 
PART XL 
TROCHIDAE. 
Conical, pyramidal, subglobose. turbinate, or helicoid; ap¬ 
erture entire, tetragonal or rounded, nacreous within; peristome 
generally not continuous. Operculum circular, thin, entirely cor¬ 
neous, formed of numerous gradually increasing whorls, nucleus 
central. 
Distribution—World-wide. Very many species live in the 
littoral, and laminarian zones, and many are deep sea forms. 
Fossil—Ordovician. 
Animal with head prcboscidiform; tentacles tapering, some¬ 
times ciliated; eyes on free peduncles at their outer bases; two 
more or less developed head-lobes between the tentacles; gill 
single, long and linear; sides of foot with a large neck-lappet near 
the eye-peduncle, continuous with a conspicuous side-membiane, 
bearing on its free margin from three to five tapering filaments, 
operculigerous lobe often with cirri. Sexes are sepaiate. Herb¬ 
ivorous. 
Shells differ from those of the Turbinidae chiefly in having a, 
corneous, never calcareous, operculum, which is always multi¬ 
spiral. 
Trochus (a trundling hoop for children) was first used by 
Rondelet 1558, in the sense of a top, which is an error, and com¬ 
prised a rather miscellaneous assortment of univalves. Linnaeus 
restricted the genus, but still retaining species of several very 
different families. Lamarck further restricted the group. During 
the past 60 years, Gray, the Adams brothers. Finlay, I redale and 
others have contributed much towards a systematic ariangement 
of the family. True Trochus is not represented in South Austra¬ 
lia. The large, well known onical Trochus (T . nUoficus ) found 
on the .Barrier Reef, is used for the manufacture of pearl buttons, 
and 960 tons were exported from Queensland in 1916, the value 
being £23.000. From ten tons of shell* one ton of meat is taken 
by the more careful Japanese fishermen, and this after '-icing 
smoked and dried is worth £20. 
Clanculus Montfort 1810, Conoidal or turbinate, not um- 
bilicate; whorls mostly granulose; periphery rounded or angular; 
base flat or convex; aperture contracted; columella spirally 
twisted, forming a false umbilicus, plicate throughout and term¬ 
inating in a multidentate varix; outer lip usually dentate within, 
