Crossword-Solution: LIGAMENTAL 10 letters, 1 clue 🏆 scrabble score: 13

Its form is like that of _Unio ovatus_ (_Mya ovata_ of Montague), but it is a much thicker and stronger shell; the posterior end is greatly compressed, but round; the umbones convex, remarkably thick, and deeply eroded; the inside pearly and iridescent, with a strong flesh-coloured tinge; the ligamental or hinge-plate is perfectly smooth, and rather convex; the muscular impressions are deep.

The vessels whereof it consisteth, are the umbilical vein, which is a branch of the Porta, and implanted in the Liver of the Infant; two Arteries likewise arising from the Iliacal branches, by which the Infant receiveth the purer portion of blood and spirits from the mother; and lastly, the Urachos or ligamental passage derived from the bottom of the bladder, whereby it dischargeth the waterish and urinary part of its aliment.

Shell free, regular, thin, solid, auricled, equivalve, equilateral; summits contiguous; hinge without teeth; a ligamental membrane through all the length of the hinge, besides a short, thick ligament, almost entirely internal, which fills a triangular cavity under the summits; one sub-central muscular impression.

The chitons or mail-shells, by their jointed nature, consisting of a series of pent-roof-shaped valves united by ligamental tissue, are nearly always represented in the fossil state by separate valves.

The operation of the ligament--using the word as including the whole ligamental process--is in opposition to that of the adductor muscles.