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- C5 Sequence (Lower Whitewater, Liberty)
Identification in Hand Sample
- Large species with wide hinge line containing angular to alate cardinal extremities
- Shell is considerably wider along the hinge line than anteriorly
- Shell outline is semielliptical to subquadrate
- Sulcus narrow and shallow
- Hinge line is prolonged giving acute cardinal angles
Hebertella alveata from the Waynesville Formation of Waynesville, Ohio (CMC 68971)
Wright & Stigall (2013):
- Diagnosis: Large Hebertella species with a wide hinge line containing angular to alate cardinal extremities. Shell widest along the hinge line, outline semielliptical to subquadrate; sulcus narrow and shallow; dorsal valve variably inflated, with a broad medial depression extending from the beak to the commissure; dorsal umbo located proximal to the hinge line, not extending significantly beyond the hinge line. Emended from Foerste (1909a).
- Remarks: Hebertella alveata occurs most commonly alongside H. occidentalis and H. richmondensis in the Liberty Formation, yet is easily distinguished by its biconvex profile, maximum shell width developed at the hinge line, pronounced angular to alate cardinal extremities, and a medial depression on the dorsal valve that extends to the commissure.
Davis (1998) :
- Sulcus in its dorsal valve runs to the anterior margin and a long ventral interarea; Richmondian strata.
- I have seen the type specimens of these species. Hebertella alveata at the U.S. National Museum (USNM 78452, 87146, and 87158, a total of seven specimens) is characterized by a distinct and broad median depression on the brachial valve extending to the anterior margin; most specimens have alate cardinal extremities. Foerste (1909a) applied the name H. alveata richmondensis to similar forms having a less distinct median depression, narrower hingeline, and more convex brachial valve. He found this subspecies to be dominant over typical H. alveata at some horizons in beds of the Whitewater Formation. H. alveata occurs in the Liberty and Whitewater Formations of Ohio and Indiana. I consider H. alveata to be a distinct species, but none of the type specimens show interiors to confirm the generic identification.
- A H. occidentalis with a distinct and broad median depression extending from the beak to the anterior margin of the brachial valve. In the types the hinge line is prolonged giving acute cardinal angles. For the associated form with rounded cardinal angles and hinge line less than greatest width of shell. Foerst (1909, p. 224) has proposed the varietal designation richmondensis.
- In typical Hebertella alveata (this Bulletin, vol. XIV, plate IV, fig. 8A), the shell is considerably wider along the hinge-line than anteriorly, the postero-lateral angles being acute.