{ V. Stump-headed { 11. Tube-snails 11. Scaphopoda III. { _Perocephala_ { 12. Butterfly-snails 12. Pteropoda =Snails= { { { 13. With hind gills 13. Opisthobranchia +Cochlides+ { { 14. With fore gills 14. Prosobranchia or { VI. Large-headed { 15. Swimming-snails 15. Heteropoda +Gasteropoda+ { _Delocephala_ { 16. Beetle-snails 16. Chitonoida { { 17. Snails with lungs 17. Pulmonata VII. Chamber-Poulps { 18. Pearl boats 18. Nautilida IV. with four gills { 19. Ammon’s horns 19. Ammonitida =Cuttles= } _Tetrabranchia_ { or } =Poulps= } VIII. Ink-Poulps with { 20. Ten-armed 20. Decabrachiones } two gills { +Cephalopoda+ } _Dibranchia_ { 21. Eight-armed 21. Octobrachiones ---------------------------------------------------------------- Dibranchia Heteropoda | | _Prosobranchia_ | _Pulmonata_ | | Tetrabranchia | Lipobranchia | | Cephalopoda | | | | (=Cuttles= or =Poulps=) | Gymnobranchia | | | | | \-------v------/ | | | | | | Pleurobranchia | Chitonides | | _Opisthobranchia_ | | | | | | | | \---------------------------------v---------/ | | | _Delocephala_ | | | | | \--------v----------/ | | _Pteropoda_ Inclusa | | | | | | \------v-----/ Sinupalliata | | Scaphopoda | | | | Integripalliata \---v--/ Sclerobrachia _Siphoniata_ | | | _Perocephala_