ANIMAL OF NASSA. 19 
track indicating their line of march, at the end of which is a small 
round pellet; under this the creature conceals itself. The 
fry twist and twirl about by means of their ciliated lobes. N. 
mutabilis is used in Italy as an article of food and supplies the place 
of our periwinkle in the markets. 
REFERENCES TO ANIMALS OF NASSA. 
Voy. del Astrolabe. 
N. tenia, Gmel. Quoy and Gaim., pl. 32, f.13. Operculum, f. 15. 
Kyes situated at about 4 the length of the tentacles from 
the base ; foot large, expanded, tapering to a point at its 
posterior extremity (not bifid), with two caudal filaments. 
N. coronata, Brug., pl. 32, f. 8. Operculum, f. 10. Eyes near the 
base of the tentacles; foot expanded, bifid at its posterior 
extremity, a filament on each side of the serrated operculum. 
N. arcularia, Linn., pl. 32, f. 1. Operculum, f. 4. Eyes situated 
about ¢ the length of the tentacles from the base; foot 
bifid ; caudal filaments not present in the figure. 
N. margaritifera, D’k’r., pl. 32, f. 16. Eyes + of the length of the 
tentacles from the base ; foot bifid ; operculum serrated. 
A second description ; foot quadrate below, broader in front than 
behind, colour milk-white, sub-pellucid behind, bifid, forming 
an angle of about 45° at the end ; siphon short, truncate, 
cylindrical and grooved, bluish ; eyes on a broad expansion 
of the tentacles. 
N. bullata, Marr., pl. 32, £5. Eyes near the base of the tentacles ; 
foot bifid ; operculum crenated. 
N. fasciata, Lam., pl. 32, f. 18. Operculum, f. 21. Eyes near the 
base of the tentacles ; foot strongly bifid ; operculum semi- 
ovate, serrated. 
N. thersites, Brug., pl. 52, f. 22. Eyes at about 4 of the length of 
the tentacles from the base ; foot bifid; operculum ovate, 
nearly plain (abnormal), serrated at the base (normal). 
N. pulla, Linn., globosa, Quoy and Gaim., pl. 32, f. 25. 
Operculum, f. 27 (abnormal). Eyes at the base of the 
tentacles ; foot bitid; operculum sharply serrated, sub- 
trigonal. 
Voy. la Bonite 
N. nodifera, Powis, pl. 41, f. 2 Eyes near the middle of the 
tentacles ; foot bifid ; operculum serrated, 
