S.A. NAT., VOL. XIV. 
August 31st, 1933. 
1.3J. 
SOUTH AUSTRALIAN SHELLS. 
(Including descriptions of new genera and species) 
PART VIIL 
{By Bernard C. Cotton & F. K. Godfrey). 
SCAPHOPODA. 
The name signifies scoop-footed. “Tusk Shells'' or “Tooth 
Shells/’ from their suggestive shape, are immediately dis- 
tinguishable from the shells of all other living molluscs, being 
straight or slightly curved tubes, without a spire. Bilaterally sym- 
metrical molluscs with the shell (and mantle) a long, more or 
less curved, tapering or fusiform tube, open at both ends, 
the concave side dorsal; anterior orifice larger, contracted by a 
muscular thickening of the mantle, and giving egress to the cyl- 
indrical head and the iong, pointed foot, which is capable of 
being enlarged and variously modified in shape distally; the 
smaller (posterior) orifice of the mantle and shell giving exit to the 
refuse of digestion, respiration and the genital products. Head 
with terminal mouth surrounded by a rosette of lobes; no eyes: 
otocysts present; no tentacles, but a close cluster of thread-like, 
distallv enlarged appendages known as captaculae, springs from 
the base of the snout. Jaw and radula present; liver two-lobed_, 
s\-mmetrical; gut strongly convoluted, the anus opening rather 
far forward in the mantle cavity, kidney openings near It, Gonad 
simple, opening through the right nephridium. Xo gills, respir- 
ation being performed by the general integument. Heart rudi- 
mentary, with only one chamber, auricles and reno-perioardial 
ducts wanting. Nervous system with well-developed ganglia* the 
cerebral, pleural, pedal, visceral and buccal ganglia symmetrlcaL 
Marine burrowing molluscs, living partially embedded In sand or 
mud on the sea bottom, with but, as a rule, the posterior ex- 
tremity projecting. They feed on the lowest organisms. Sexes 
distinct. The tubular shell, open at both ends, is characteris- 
tic of the group, and occurs nowhere else in the mollusca. Growth 
takes place at the larger end and on the inside of the tube, and at 
the same time the shell is absorbed at a slower rate from the 
smaller end. The slits and notches in this end are therefore 
formed by absorption, being wholly different in genesis from 
similar structures of the peristome in Gastropods. In some forms 
upon the practical cessation of growth and absorption upon the 
