226 
HORN EXPEDITION—MOLLUSCA. 
Lipapus spencepi, Tate. 
Several drowned specimens from Palm Creek were examined. Jaw (Fig. N) 
unsymmetrically arched, three times as long as broad, brown, with numerous dark 
longitudinal lines arranged as in an agate ; trans¬ 
lucent, thin, thinnest on the convex, thicker on the 
concave margin. Folded into nine pleats on the 
richt and seven on the left towards a central 
triangular area, which does not reacli the lower 
margin, denticulating the lower but not the upper 
margin; seen in front the free edge of the fold is nearest the jaw’s centre. This 
jaw is straighter, with fewer pleats than either that of Z. mnstersi (Pro. Koy. 
Soc. Qland., VI., PI. XIV.) or that of Z. iasmanims (P.L.S. N.S.W., 2, VI., PI. 
II., f. 2). 
Radula (Fig. O) two-and-a-half times as long as broad j rows nearly straight, 
crossing the ribbon squarely. Formula 113 rows of 32 : 15 : 1 : 15 : 32. 
Rachidian base rather longer than bi'oad, slightly expanded anteriorly ; reflection 
tricuspid, consisting of a large ovate mesocone, a little shorter than the basal plate 
and two minute side cusps, the latter a Buliminoid feature to be expected, but not 
previously recorded in this genus. Laterals larger, with entocone suppressed; 
ectocone developed and mesocone broader than the rachidian. Transition teeth 
decrease rapidly in size, with a slender mesocone less inclined to the rachidian. To 
the remotest marginals the mesocone dominates the ectocone. 
f. 14. 
Tentacle retracted to the right, not between the 
branches of the genitalia (Fig. P). Penis sac without 
papilla, ridged within, very long, much coiled, and 
tapering slowly. Vas deferens free beneath, above 
bound to wall of penis sac. Retractor muscle 
extremely slight, attached to the membrane envel¬ 
oping the uterus. Spermatheca oblong, seated on a 
very long and tortuous duct which follows the con¬ 
volutions of the uterus. This system agrees with 
Semper. Reis, im Phil. Band, III., p. 154, PI. XV., 
