uliginose, uliginous a. [L. uliginosus, swampy] Of or pertaining to mud; swampy.

ultradextral a. [L. ultra, beyond; dexter, right] (MOLL: Gastropoda) Having a shell appearing to be sinistral but soft parts organized dextrally; hyperstrophic.

ultrasinistral a. [L. ultra, beyond; sinister, left] (MOLL: Gastropoda) Having a shell appearing to be dextral but soft parts organized sinistrally; hyperstrophic.

ultrasonic a. [L. ultra, beyond; sonus, sound] High frequency sounds inaudible to the human ear.

ultrastructure n. [L. ultra, beyond; struere, to construct] The fine structure of cells seen with an ultramicroscope or an electron microscope.

umbel n. [L. umbella, a sunshade] 1. An arrangement in which a number of processes, nearly equal in length, spread from a common center. 2. (CNID: Anthozoa) In Umbellulidae, polyps coming from a common center, forming a cluster, as in the anthocodia of Umbellula . 3. (porif) Processes extending from the clavules.

umbilical suture (MOLL: Gastropoda) In phaneromphalous type shells, a continuous line separating successive whorls.

umbilicus n.; pl. -lici [L. umbilicus, navel] 1. A navel, or navel-like depression 2. (MOLL: Gastropoda) A cavity formed around the shell axis between the faces of the adaxial wall of the whorls where these do not coalesce to form a solid columella. a. In conispiral shells opening at the base of the shell, excepting hyperstrophic type. b. Involute shells may have two umbilici, an upper or adapical and lower or abapi-cal in asymmetrical types, and left and right in isostrophic types. umbilicate a.

umbo n.; pl. umbones, umbos [L. umbo, knob or boss] 1. (ARTHRO: Crustacea) a. In Cirripedia, a portion of the plate from which successive growth increments extend. b. In bi valves, apical portion of either valve. see beak. 2. (ar-THRO: Insecta) In Coleoptera, an elevated knob on the humeral angle of the elytra. 3. (BRACHIO) Apical portion of either valve containing the beak. 4. (BRYO: Gymnolaemata) In Cheilostomates, a blunt knob on the front wall of the ovicell. 5. (MOLL: Bivalvia) That region of the valve surrounding the point of maximum curvature of the longitudinal dorsal profile; when not coinciding with the beak, extending to its base. umbonal a.

umbonal angle (MOLL: Bivalvia) In pectinoid shells, the angle of divergence of the umbonal folds; in other shells the divergence of the posterodorsal and anterodorsal parts of the longitudinal profile.

umbonal cavity (MOLL: Bivalvia) 1. Part of the valve interior which lies within the umbo and under the hinge plate. 2. In oysters, that part of the left valve interior lying in the umbonal region beneath the ligamental area.

umbonal depression (MOLL: Bivalvia) A depression at the umbo tip.

umbonal fold (MOLL: Bivalvia) In pectinoid shells, a ridge originating at the umbo and setting the auricle off from the shell body.

umbonal pole (MOLL: Bivalvia) The point of maximum curvature of the longitudinal profile of the dorsal valve.

umbonal reflection (MOLL: Bivalvia) The reflection of the dorsal margin of the valves anterior to and usually over the umbos.

umbonal region (MOLL: Bivalvia) The region of the umbo.

umbonal spine (ARTHRO: Crustacea) In Conchostraca, a hollow, curved, looped or nodular spinose projection of variable size, sometimes covering the entire umbo.

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