Monography of the family Unionidæ : or, Naiades of Lamarck (fresh water bivalve shells) of North America ... . Unto pffCusit^, Lam 19UNIO RETUSUS. Plate Shell transversely ovate, ventricose, with concen-tric furrows; umbo very prominent, curved forwards;beaks retuse, medial; ligament long and prominent;umbonial slope rounded, undefined; anterior and basalmargins regularly rounded; posterior side with aslight furrow, and emarginate at the extremity; liga-ment slope arcuate, very oblique; within dark purple,margined with white. SYNONYMES. U. retusa, Lam. An. sans vert. vol. vi.
Monography of the family Unionidæ : or, Naiades of Lamarck (fresh water bivalve shells) of North America ... . Unto pffCusit^, Lam 19UNIO RETUSUS. Plate Shell transversely ovate, ventricose, with concen-tric furrows; umbo very prominent, curved forwards;beaks retuse, medial; ligament long and prominent;umbonial slope rounded, undefined; anterior and basalmargins regularly rounded; posterior side with aslight furrow, and emarginate at the extremity; liga-ment slope arcuate, very oblique; within dark purple,margined with white. SYNONYMES. U. retusa, Lam. An. sans vert. vol. vi. p. 72. Ferus. Mag. de torsa, Raf. Ann. gen. ties Sc. Phys. vol. v. p. 45. pi. lxxxii. fig. 1, 2, 3. Poulsons trans, p. 40. OBSERVATIONS. This fine species is remarkable for the elegance ofits form, and the prominent curved beaks whichsomewhat resemble those of an Isocardia. The colourof the nacre is remarkably constant. One variety isdeeply sulcated and emarginate posteriorly; anotheris entire. Young shells much resemble U. subrotun-das, Raf. Common in the western waters. I didnot observe it in A
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Keywords: ., bookcentury1800, bookdecade183, booksubjectmollusks, bookyear1836
