THE MOLLUSCA—HEDLEY. 427 
Beneath the head is a flap terminating anteriorly in two pro- 
cesses and arising from a deep cleft between the mouth and the 
operculum. Treating of the same or an allied species from Guam, 
Quoy and Gaimard* describe this as an anti-buccal appendage and 
figure it from above. I regard it as the relic of a degenerated 
propodium. The accompanying sketch (Fig. 17) in profile, of an 
animal half drawn out of the shell and stript of the operculum, will 
better convey an idea of this organ than figures taken from above. 
Fig. 17. 
Whena gasteropod retreats into the shell it doubles the foot either 
lengthwise, as in some inoperculate forms, or across, as in most oper- 
culates. In the latter case when completely retracted, the foot is so 
folded head to tail that the anterior half of the sole is applied to the 
posterior; the operculum then closes the aperture. In a sedentary 
form this position of retraction might become permanent. Where 
the foot never serves for progression, but continues to maintain a 
useful operculum, it is easy to imagine that the fore part of the 
folded foot would become atrophied and that as it diminished the 
hind part would enlarge. This is the history suggested for the 
shrunken propodium of Vermetus, which lies tucked away between 
the mouth and the operculum. The process of evolution perhaps 
continued in the direction of utilising the appendices of the pro- 
podium as tentacles. 
This species was collected by Hugh Cuming at Marutea, Pau- 
motus, and opercula of it were received from Lifu by Melvill and 
Standen. In a preceding article (p. 243) I have quoted a descrip- 
tion of a mollusc from Mangaiia, called “ ungakoa,” which is 
probably this. In Java it is known as “karang,” which Morch 
translates as “coral tube.” The only Pacific shell with which 
this can be confused is the pipe-like Kwphus arenarius, L. 
VERMETUS, Sp. 
A second species of this genus, somewhat resembling V. grandis, 
Gray,} or V. imbricatus, Dunker, also occurred. 
TURRITELLA CONCAVA, Martens. 
Tryon, Joc. cit., p. 206, pl. Ixiv., fig. 6. 
*Quoy & Gaimard—Voy. “Astrolabe,” Zoologie, iii., 1835, p. 295, pl. 
Ixvii., figs. 13 - 15. 
+ Tryon—Man. Conch., viii., 1886, p. 182, pl. liv., fig. 79. 
