462 ON TILE ANATOMY OF PONTIOTHAUMA. 
EXPLANATION OF PLATE 42. 
Fig 1. Pontiothauma mirabile,8m. External view of animal as contracted in 
spirit. 
. Pontiothauma mirabile, Sm. Rostrum as seen from the front. 
3. Pontiothauma mirabile, Sm. General dissection of the pallial chamber, 
rostrum, and body-cavity ; the poison-gland is omitted. 
4. Pontiothauma mirabile, Sm. Tissection of the introvert and anterior 
region of the alimentary canal; the salivary glands and the distal 
portion of the poison-gland are omitted. f 
Figs. 5, 6,7. Pontiothauma mirabile, Sm. An isolated tooth of the radula 
viewed from different directions. 
Figs. 8, 9. Pontiothauma mirabile, Sm. The terminal portion of a tooth more 
highly magnified to show its external opening and barbed extremity. 
Fig. 10. Pontiothawma abyssicola, Sm. External view of the animal as preserved 
in spirit. 
11. Pontiothauma abyssicola, 8m. General dissection, showing the rela- 
tionships of the introvert apparatus, alimentary canal, &c. The 
poison-gland is seen in its undisturbed position to the right of the 
to 
cesophagus. 
12. Pontiothauma abyssicola, 8m. Median vertical section through the 
rostrum and anterior portion of the body-cavity ; the poison-gland, 
radula-sac, &c. are omitted. 
13. Pontiothauma abyssicola, Sm. Portion of the alimentary canal viewed 
from below, showing the relationships of the radula-sac, salivary 
glands, and poison-gland. 
14, Pontiothauma abyssicola, Sm. An isolated tooth of the radula. 
Abbreviations. 
B.M. Pharyngeal bulb. Oe. CGisophagus. 
C.M. Columella muscle. Os. Osphradium. 
Ct. Ctenidium P. Penis. 
D.Gl. Digestive gland. R. Rectum. 
F. Foct. R.M. Retractor muscle of the 
Hy.Gl. Hypobranebial gland. introvert. 
I. Introvert. R.S. Radula-sac. 
LS. Introvert sheath, Rh.’, Rh.” Anterior and _ posterior 
K. Renal organ. chambers of the rhynchodxum. 
L.Gl. Leiblein’s gland: “ poison- S. Siphon. 
gland.” $.G]. Salivary glands, 
M.L. Mantle-lobe. St. Stomach. 
N. Central nervous system. 
