HORN EXPEDITION—MOLLUSCA. 
223 
conjoined uterus and spenuatlieea duct in an unusual way. Tlie spennatheca duct, 
wliicli ends in a globose head, is bent like the letter Z before reaching its desti¬ 
nation. 
Xanthomelon fodinalis, Tate. 
Two examples from Palm Creek were dis¬ 
sected. The jaw (Fig. (x) is crossed by a dozen 
ribs, well developed in the centre, but evan¬ 
escent at the sides. These denticulate both 
margins, and are divided by deep interstices of 
half their breadth. 
The radula (Fig. H) has for formula 140 transverse rows of 3G : 12 ; 1 ; 12 : 
3C. Rachidian a single ovate cusp shorter than the basal plate. Rudimentary 
side cusps appear to be indicated at its base. Laterals longer and stouter. Tn the 
transition teeth the ectocones appear two or three rows before the entocones. The 
marginals show a sharply-pointed ectocone and a blunt longer mesocone united at 
half its length to the entocone. 
In the genitalia (Fig. I.) the right tentacle is reti’acted between the branches. 
Spennatheca oval, seated on a very short twisted duct. Vagina short. Vas deferens 
having ascended the penis for 
half its length, describes a free 
loop and then plunges into the 
wall of the penis sac. On open¬ 
ing the latter the vas deferens 
is recovered after having tunn¬ 
elled the integument for a 
quarter of its length. It then 
takes a half turn round the 
