Carpal sucker - The suckers of the carpal locking-apparatus.
Carpal knobs - The knobs of the carpal locking-apparatus.
Carpal locking-apparatus - The region at the base of the tentacular club which has small suckers and knobs. The carpal locking apparatus often extends from the dorsal margin of the manus on to the distal region of the tentacular stalk. The region of the tentacle that contains the carpal locking-apparatus is sometimes called the carpus. This term, the carpus, is most appropriate where the carpal locking-apparatus is separate from the manus (e.g., Onychoteuthis spp.). In some species the locking apparatus extends down most of the length of the stalk. The locking mechanism involves the carpal suckers and knobs of one tentacle adhering to their counterparts on the opposite tentacle which, thereby, holds the clubs together at their bases. To visualize this from a human perspective, imagine your wrists joined together while you reach for something with fingers and palms spread apart.
Drawing: Club of Leachia dislocata, modified from Young, 1972.
Dactylus - The narrow, distal portion of the tentacular club of some decapodiforms. The dactylus is often characterized by the asymmetrical placement of suckers (i.e., the ventral expansion of the club) and the absence of a dorsal protective membrane.
Dorsal keel - A vane that extends dorsally from the tentacular club of many species. The keel arrised distally from the dorsal margin of the dactylus and proximally terminates at various points on the aboral surface of the manus depending on the species. The dorsal keel may parallel the dorsal protective membrane or may extend to the mid-aboral surface of the manus. The keel, presumably, has a hydrodynamic function.
Manus - The proximal, broad portion of the tentacular club in many squids which is generally expanded equally on both dorsal and ventral margins and often includes enlarged suckers.
Stalk of the tentacle - The tentacle proximal to the club. The stalk is usually bare of armature but in some species it carries suckers and knobs (i.e., the carpal locking-apparatus) and in few species, suckers without knobs.
Tentacular club - Terminal, usually expanded, grasping portion of tentacle that is armed with suckers or, in some groups, with suckers and hooks.
Terminal pad of the tentacular club - A circlet or disc composed of small suckers at the tip of the tentacular club. The pad is usually associated with a narrow membrane that encircles the distal edge of the pad and fuses with the dorsal keel. The pad of one club can adhere to the pad of the other club to insure that the clubs reach their target simultaneously. This has been clearly demonstrated in Loligo (Kier, 19xx) and presumably is true of all species with a pad. To visualize this from a human perspective, imagine touching, and holding, your finger tips from both hands together with palms turned outward while you slap the open palms against a wall.
Information is available on the variation of these structures in different decapodiforms.