Page 121 - The Freshwater Mussels of Oklahoma

Partial Synonymy:
Quadrula trapezoides (Lea, 1831), Simpson 1914; Isely 1925
Plectomerus trapezoides (Lea, 1831), Isely 1925
Plectomerus dombeyana (Valenciennes, 1827), Oesch 1984
Plectomerus dombeyanus (Valenciennes, 1827), Johnson 1980; Branson 1982;
Turgeon and others 1988; Vidrine 1993; Howells and others 1996
Description:
“Shell long rhomboid, subinflated to inflated, solid, inequilateral; beaks only
moderately full and high, their sculpture consisting of a few decidedly nodulous
corrugations; posterior ridge strong and high, often pinched up into a sharp angle, ending
at the base of the shell in a point; anterior end a little narrowed and rounded; base line
straight; post-dorsal area somewhat winged; posterior end obliquely truncated with a
slightly curved outline; surface with a few oblique folds in front of the posterior ridge and
on the posterior end there are curved folds; umbonal region with lengthened nodules
arranged in zigzagged patterns; epidermis brownish or blackish; pseudocardinals ragged,
radially split; laterals long; muscle scar large, the anterior ones filled with roughened
nacre; beak cavities moderately deep; pallial line remote; nacre purple-red” (Simpson
1914, p 830).

Table 22. Summary of P. dombeyanus shell characters.

Maximum
Mean H/L H/L Range Length Mean H/L W/L Range
Location N (%) (%) (mm) (%) (%)
Red River Drainage
Glover River 2 60.3 59.6-60.9 115 39.1 33.0-45.2
Little River 25 56.5 50.7-65.6 116 32.3 25.6-42.7

General Distribution:
Lower Mississippi River drainage and adjacent Gulf of Mexico tributaries from
eastern Texas through Mississippi.
Oklahoma Distribution:
Found only in the lower Little River and Glover River.

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