Key to the Orders and Sub-Orders of Cephalopods a

KEY TO THE ORDERS AND SUB-ORDERS OF CEPHALOPODS A. Shell internal or absent ; arms, eight to ten ; gills, two.

Order DI BRANCH! ATA B. Arms eight, all alike ; suckers fleshy ; shell absent.

Sub-order OCTOPODA Eight-armed Cephalopods The Argonauts The Devil-fishes BB. Arms ten, two elongated; suckers with horny rims; shell internal.

Sub-order DECAPODA Ten-armed Cephalopods The Spirula The Cuttles The Squids AA. Shell external ; arms, more than ten; gills, four.

Order TETRABRANCHIATA, The Chambered Nautilus 440