NILS HJ. ODHNER, PTISANULA LIMN^OIDES. 17 



1906. Vayssiére, A., Recherches zool. et anat. sur les Opistbobr. de 

 la Mer Rouge etc. Ann. Faculté de Sci. Marseille. Torne IG. 



1883. Watson, R. B., Mollusca of H. M. S. 'Cballenger' Exped. 

 Part XVIII. Journ. Linn. Soc. Zool. Vol. XVII. London. 



Explanation of the Plate. 



1. Ptisanula limnceoides, fossil sbell from Kapellbacken, at 

 22 m above the sea; spire somewhat broken. X 10 and 

 nat. size. 



2. The same, a recent shell from Bel Sound, 5 — 12 fms, seen 

 from aperture and from back; cuticula removed. X 10 and 

 nat. size. 



3. The same from Horn Sound, with cuticula and withdrawn 

 animal. X 10 and nat. size. 



4. The same, fossil, from Kapellbacken at 26 m above the 

 sea. X 10 and nat. size. 



5. Scheme of the organisation of Ptisanula. f median furrow 

 in which the foot gland opens, behind the pharynx, int in- 

 testine, m mouth, oc eye, p penis, ph pharynx, J\ $ ma l° 

 and female genitale pore. Nervous system black. 



6. Radula of Ptisanula limncBoides; some teeth from the side; 

 the lam. laterales cover the median teeth. X 325. 



7. Transversal section of the radular sheath; Iö^ lam. laterales. 



8. Radula, seen somewhat from below; under the median teeth 

 the lam. laterales of the left side are seen from outside. 

 X 325. 



9. Genital apparatus of Ptisanula limnccoides. p penis. 



10. Penis of Diaphana glacialis in its sheath. 



11. Genital apparatus of Diaphana glacialis. gl albumen gland, 

 p penis, sp spermatocyst, J* hermaphrodite gland with its 

 ductus deferens (duct), J oriiice of the vagina, J* orifice of 

 the penis sheath. 



Fig. 12. Transversal section of the stomach of Ptisanula. cut cuti- 

 cula, m muscular layer. 



Fig. 13. Horizontal section through the eye of Diaphana glacialis. 

 c cerebral ganglion, gangl diffuse olfactory ganglious layer, 

 ii nerve, oc eye, ol proximal or tentacular ganglion. X 185. 



Fig. 14. Frontal section through the eye of Ptisanula. a chroma- 

 tophores, oc eye. X 185. 



Figs. 15 — 17. Scheme of the combination of optic and tentacular 

 nerves in Actccon (Fig. 15), Ptisanula (Fig. 16), and Dia- 

 phana (Fig. 17). c cerebral ganglion ; cct ectoderm, gangl 

 diffuse olfactory ganglious layer, oc eye, tent tentacular nerve. 



År/riv fur zoologi. Band 8. N:o 25. 2 



