CEPHALIC APPENDAGES OF GYMNOSOMATOUS PTEROPODA. 507 
Pneumodermon, and Cirrifer (compare figs. 2, 4, and 7) 
The “lips" situated between the cones of Clione are not 
then equivalent to the lips of the other Gvmnosomata, in 
which there is no developed hood like that of Clione. 
They would be a differentiation of the internal wall of the 
buccal cavity, which is produced behind the buccal appendages. 
In this manner we see that with Clione, as with Pneu- 
modermon and Cirrifer, the buccal appendages are inserted 
on the internal wall of the buccal cavity. 
At the same time it must be remembered that this front 
portion of the buccal cavity may be regarded as not part of the 
true oral cavity, but as only an “ introvert ” like that of pro- 
boscidiferous Gastropods. 
EXPLANATION OF PLATE XXXV. 
Illustrating Dr. Paul Pelseneer’s Paper on “ The Cephalic 
Appendages of the Gymnosomatous Pteropoda, and espe- 
cially of Clione/’ 
Fig. 1. — Head of Clione. Dorsal aspect, a. Labial tentacles, b.. Nuchal 
tentacles, c. Buccal cones, d. Fins. e. “Lips.” /. Edge of the hood. 
Fig. 2. — Head of Clione. Oral view, the hood being nearly closed, a. 
Labial tentacles, c. ^Buccal cones. /. Edges of the hood. 
Fig. 3. — Head of Clione. Lateral view. a. Labial tentacle, b. Nuchal 
tentacle, c . Buccal cones, d. Fin. e. Foot. /. Edge of the hood. g. 
Orifice of the penis. 
Fig. 4. — Head of Clione. Oral view, the hood being open. a. Labial 
tentacles, c. Buccal cones, d. “ Lips.” f. Edge of the hood. 
Fig. 5. — Head of Clionopsis. Dorsal aspect. 
Fig. 6. — Head of Clionopsis. Lateral view. a. Labial tentacles, b. Nuchal 
tentacles, c. Foot. d. Fins. e. Orifice of the penis. 
Fig. 7. — Head of Clionopsis. Oral view. a. Labial tentacles, b. Mouth. 
e. Lips. 
