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Synonyms: Orthis occidentalis
Synonyms: Orthis occidentalis
Map point data provided by iDigBio.
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- C6 Sequence (Elkhorn, Whitewater)
- C5 Sequence (Liberty, Waynesville)
- C4 Sequence (Arnheim)
- C3 Sequence (Mount Auburn, Corryville)
- C2 Sequence (Bellevue, Fairview: Fairmount, Mount Hope)
- C1 Sequence (Economy/Fulton)
Identification in Hand Sample
- Moderate to larger Hebertella species
- Moderate to highly pronounced sulcus
- Convexoconcave or unequally biconvex
- Ventral and dorsal umbonal angles low (<135 degrees)
- Elevated, straight and not incurved beak
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- Moderate to large Hebertella species with a subquadrate outline and a moderate to highly pronounced sulcus. Shell wider than long; shell depth variable, convexoconcave to unequally biconvex; cardinal extremities angular; sulcus wide with moderate to very high depth, typically well developed in larger specimins; ventral muscle scars of variable width; dorsal and ventral umbonal angles low (<135 degrees). Emended from Hall (1847).
- Articulate brachiopod. Fig. 2, exterior of brachial (dorsal) valve. Fig. 3, interior of pedicle valve with triangular pedicle opening. Note the trilobed, central muscle impression. Fig. 4, the relatively flat pedicle valve with the raised beak. Fairmount up into the Richmondian.
- Shells frequently 30-35 mm wide. Brachial (dorsal) valve strongly convex, frequently with a median fold anteriorly. In typical forms a faint depression along the median line near the beak. Hinge-area of pedicle valve diverges strongly from the plane separating the valves. Radiating plications numerous, secondary plications being intercalated among primary ones in more or less alternate order. Muscle impression in interior of pedicle (ventral) valve ovate-oblong in outline, deeply impressed, and tending to be heart-shaped along its lower margin.
- H. sinuata (Hall) differs chiefly in the greater coarseness of the radiating plications, especially the primary ones, before the intercalation of addition plications begins.
- Locality and Horizon. In Ontario and Quebec relatively rare in the Lorraine, but listed in the Proetus zone, form Hawthorne and Ramsayville. In the Pholadomorpha zone, form the Nicolet River section; also south of Clay cliffs. Abundant in the Meaford at Gore Bay, Kagawong, south of the Little Current, at Manitowaning, Clay cliffs (No. 8510), Meaford, Oakville, Streetsville, Vars, on Huron river, in the Nicolet River section (No. 8439), and on Snake island. In the Kagawong member of the Richmond formation, it occurs at Manitowaning and est of the Indian Village southwest of Little Current.
Paleontology of New York (1847):
- Resupinate, transversely somewhat oval, or longitudinally semioval ; length and breadth about as 5 to 7 ; cardinal line equal to the greatest width of the shell ; area large, triangular, partially common to both valves ; foramen narrow, triangular, reaching to the apex of the dorsal valve ; dorsal valve convex towards the beak, and usually flattened or slightly convex towards the margin (in old shells a broad depression in front) ; beak much elevated, straight, not incurved ; ventral valve regularly convex, with a slight depression along the centre ; beak slightly projecting beyond the cardinal line, and incurved ; surface marked by subangular radii, which bifurcate at one-half or two-thirds the distance from beak to base ; radii crossed by fine sharp elevated concentric lines, which are usually well preserved in the spaces between the radii.
- This species, in some of its phases, approaches in general aspect to the last, but differs in essential particulars. The length from beak to base is proportionally less than in the last ; the depth of the two valves together, when not compressed, is greater ; the beak of the dorsal valve is more elevated, the area larger and foramen longer ; the beak of the ventral valve is likewise a little more incurved ; the radii are stronger, and do not bifurcate near the beak ; the concentric elevated lines are sharper and finer ; the striae are straight and direct, the last ones not bending upwards as in the O. subquadrata. As the shell becomes advanced, the dorsal valve presents an increasing depression towards the margin, which finally becomes a broad, not distinctly defined sinus. At the same time the slight depression in the centre of the ventral valve, similar to that in the last species, does not reach the margin, and finally becomes obsolete. The slight elevation in front, shown in the last, is exactly reversed in this species.
- These characters, when once observed, will not fail in enabling the student to identify the species, and to distinguish it from any others in the same geological position. The internal structure is not as well known as in the last, the interior of the dorsal valve not having been seen. The interior of the ventral valve corresponds in general character to the last ; the small medial ventral tooth does not, however, reach as high as the plane of the area, and it is thin and sharp, while the last’ is thick. The interior surface is marked nearly to the beak with the impressions of the external radii ; while in the last, these markings reach only a short distance from the margin.