Alasmidonta raveneliana

Shell subovate or kidney-shaped, rather thin but not fragile; anterior margin sharply rounded; ventral margin straight or concave; posterior margin roundly pointed ventrally and obliquely flattened above; dorsal margin posterior to beaks nearly straight, slopes into anterior margin before beaks; beaks positioned in anterior 30% of shell length, project only slightly above hinge line, sculpted with approximately seven moderately heavy ridges the first few of which are indented towards the beak; posterior ridge prominent, rounded, somewhat double and flattened near posterior margin in some larger shells, maximum of shell width along posterior ridge near center of shell; posterior slope moderately wide and slightly concave; periostracum roughened only by growth lines, yellowish-brown to dark brown, green rays may be absent to prominent particularly in the posterior portion of the shell. Pseudocardinal teeth small, pyramidal, compressed, single in each valve; interdentum of left valve reflected upwards into moderately-sized projection; lateral teeth absent; beak cavity shallow; anterior muscle scars confluent, impressed; posterior muscle scars confluent, lightly impressed; pallial line complete, impressed; nacre whitish to bluish white, shiny, beak cavity often with pinkish to brownish coloration, may be blotched with brown (adapted from Clarke, 1981)

A thin, elongate shell with a rounded posterior ridge and no sculpture on the posterior slope. Hinge dentition is fairly typical for ALASMIDONTA: no lateral teeth, the interdentum reflected into a tooth-like structure in the left valve, and small, rather compressed pseudocardinals. The closely related ALASMIDONTA MARGINATA and A. ATROPURPUREA have relatively higher and more accurately angled posterior ridges and corrugated sculpture on the posterior slopes. Neither of these two species occur sympatrically with A.RAVELENIANA. ALASMIDONTA RAVELENIANA and A.VIRIDIS do occur together, but the latter species is a smaller, more quadrate shell, has heavier dentition, and sometimes displays partially developed lateral teeth. Hight: 35mm.

This species is found in shallow, medium sized-creeks and rivers with clear, well-oxygenated moderate to fast flows at shallow water depths, often in riffles and runs, with stable coarse sand and gravel substrate with cobble, boulders, or bedrock present (USFWS 1994; 1996; 2002).