shell

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shell

(shel),
An outer covering.

shell

Etymology: AS, scell
1 a hard outer protective covering that encloses material.
2 a principal energy level occupied by an electron in an atom.

shell

(shel)
An outer covering.

shell

any hard outer covering, such as the carapace of turtles and tortoises, the exoskeleton of crustaceans, the calcareous plates of echinoderms, the outermost membranes of an egg, the skeleton of Foraminifera or the mantle secretions of molluscs.

impression, eye

A negative form or replica of the anterior part of the eye. A substance with rapid gelling properties is held in contact with the eye until gelled. This impression (or mould) is then used in the preparation of a positive model called a cast (or casting) of the anterior part of the eye: it is made by filling the impression with a material containing a plaster of Paris base which hardens to artificial stone. Using this cast a shell of a scleral contact lens is produced with optimum shape of the back surface. Syn. impression; impression moulding; mould; ocular impression.
References in periodicals archive ?
Larvae of the pteropod Cavolinia inflexa exposed to aragonite undersaturation are viable but shell-less.
The approach uses a shell-less chick embryo model implanted with human cancer cells.
Newborn, free-swimming, microscopic, shell-less, eyed larvae are quickly placed in a special, warm tank in the hatchery to set on shell fragments, which are crushed up primarily from surf clams.
8:45 DECREASED PRESSURE AND INCREASED DEHYDRATION AS INDICATORS OF THE PROBLEMS ASSOCIATED WITH SHELL-LESS CHICK CULTURES **.
John struck a deal with tradesmen in Mexico and recently had a consignment of 29,000 shell-less coconuts shipped over to England.
04), three individuals were found shell-less, whereas a fourth was found extruding partway out of its shell (Fig.