MACGILLIVUAYIA PELAGICA AND CHELETROPIS HUXLEYI. 
293 
Explanation of Plate. 
PLATE XVL 
Fig. 1. Macgillivrayia pelagica (about three times the natural size), as it appeared 
ascending the side of the vessel in which it was placed. 
Fig. 2. Ditto, with foot expanded at the surface of the water, the ends of the branchioe 
protruding. 
Fig. 3, Ditto, the crucial gills fully exposed as the animal lay upon its side at the 
bottom of the vessel. 
Fig. 4. The four gills slightly magnified to exhibit their character more clearly. 
Fig. 5. Portion of lingual strap oi MacgUlivr ay ia. 
Fig. 6. Ditto of Cheletropis. 
Fig. 7- Labial plates of the latter. 
Fig. 8. Portion of covered gill of same. 
Fig. 9. A tentaculura, showing the anatomy of the eye. 
Fig. 10. One of the acoustic capsules containing a spherical otolithe. All the objects 
highly magnified. 
The remaining figures show the relative sizes of the shells of several species of 
pelagic Gasteropods, all of which are represented about twice the natural size. 
Figs. 11, 13 and 14 are quite new, requiring both names and descriptions. 
Fig. 12. A species of Cheletropis, probably not that of Huxley. 
Fig. 15. Macgillivrayia pelagica. 
The opercula of the respective shells are shown in the lowermost row, somewhat 
magnified, to exhibit the spiral nucleus and the lines of growth which determine 
their ultimate shape and character. 
H.M.S. ‘ Herald^ Sydney, 
February 11, 1854. 
2 R 2 
