n.1.(Zool.) The second joint of the antennæ of crustaceans.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
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2C, see 8C see later) reduced to broadly rounded lobe fitting closely to posterior concavity of transverse ocular plate; dorsal surface of carapace generally rounded, obsolescent epigastric ridge present, defined by conspicuous grooves extending from bases of antennal lobes; antennal lobes broadly rounded; branchiostegites strongly inflated; pterygostomial expansion covering greater part of antennal basicerite; ventral margin closely approximating bases of pereopods (Fig.
Antennal scale generally oval with distal margin obliquely truncate, distolateral tooth absent; dorsal surface of antennal scale with prominent middorsal carina; basicerite with acute or subacute ventrolateral tooth, lateral surface concave in proximal part to accommodate expanded pterygostomial part of carapace.
4C) not tightly fitting against antennular peduncle, with small, subacute distolateral tooth far exceeded by broadly rounded distal lamella; basicerite (Fig.
5A to C) with scattered tufts of very short setae or single setae on surface; noticeably produced pterygostomial lobe partially covering antennal basicerite, but otherwise similar to that of stage A.
6B, C) tightly fitting against antennular peduncle, without distolateral tooth but with short transverse groove distolaterally; basicerite partially covered by pterygostomial projection of carapace.
Carapace nearly as broad as pleon; dorsal surface rounded; antennal tooth weak, blunt or showing as broadly rounded lobe; anterolateral part only slightly inflated; pterygostomial expansion at most partially covering antennal basicerite; ventral margin not closely approximating bases of pereopods.
Antennal scale generally oval with distal margin broadly rounded, blunt distolateral tooth present; short transverse suture extending mesially from base of distolateral tooth; dorsal surface with prominent mid-dorsal carina; basicerite with subacute ventrolateral tooth.
9A to D) with anterior part sloping anteriorly; no longitudinal depression on either side of midline; antennal lobe broadly rounded; pterygostomial expansion directed rather ventrally, exceeding beyond tip of antennal basicerite, rounded.
12A to C) with anterior part not strongly sloping anteriorly even in spawning females; shallow longitudinal depressions, ornamented with irregular pattern of longitudinal striae, present on dorsal surface either side of midline in ovigerous females; antennal tooth showing as small, blunt prominence; pterygostomial projection directed forward, somewhat tapering distally, reaching tip of ventrolateral tooth of basicerite, terminating in rounded tip.
The antennular peduncle was always 3-segmented and the basicerite was usually present, but the statocyst was never completely formed.
Some specimens possessed 3-segmented inner and outer antennular flagella (rather than the usual 4 segments), but the peduncle was always 3-segmented, with basicerite and statocyst fully developed.