DEFINITIONS or Two NEW SPECIES OF SOUTH 
AUSTRALIAN POLYPLACOPHORA. 
By EDWIN AsHBY. 
a [Read September 3, 1900.] 
The discovery of the two new species of mollusca described in 
this paper is one of the many valuable results of Dr. Verco’s 
dredging trips. Their discovery is of particular interest, because 
genera are, as far as our present knowledge goes, very 
rly represented in any part of the globe. Only one species of 
3 enry 
. Pilsbry, in his * Manual of Conchology," says of this genus 
and its allied genera—** Of the whole series there are very few 
species known. All of them are rare” And the other sub- 
genus Stenochiton is only represented by two or three species, 
though the allied C s Stenoplax, to which the species herein 
described bears some affinity, is a little better represented ; but 
no representative has yet been recorded from this colony 
Ischnochiton (Stenochiton) pallens, sp. nov. Pl. i., figs. 1a—g. 
General Appearance.—Shell glossy, dis pig anterior portion 
tapering to rear. Evenly arched and rounded, side slope curved. 
our.—Cream, mottled with pink id pu brown. 
Anterior Valve.—Smooth and glossy, except for several growth 
lines—that nearer the outer margin being the deeper. This 
valve is longitudinally much shorter than is the case in 
Stenochiton THE and S. Pilsbryanus. Slits 13, at very irregular 
distances apart. 
Posterior Valve. — Shield - shape tapering rapidly, mucro 
posterior, only slightly raised. A deep sulcus traverses the whole 
valve a short distance from the margin, preserving the shield 
outline of the shell. A shallow diagonal depression crosses the 
valve from the mucro to the suture. Surface of shell glossy nem 
numerous growth lines, which are continued right across the 
dorsal area. The three areas are hardly distinguishable, except 
that the lateral area is slightly raised. The posterior margin is 
finely serrated like e where the valves are not worn. Four 
of the median dios k one broad wedged-shaped slit on each 
side ; two valves have two slits on each side. Inside of shell 
