STROPHOMENA. 
77 
Strophomena depressa : Vanuxem, Geol. Report Third District New-York, 1842, pa. 79, f. 5. 
S. undulata : Id. Ib., p. 139, f. 3. 
S. depressa .• Hall, Geol. Report Fourth District New-York, 1843, p. 77, f. 5; and p. 104, f. 2. 
Orthis rugosa : F. C. Rcemer, Rhein. Uebergangsgebirge, 1844, pp. 85 & 90. 
Leptcena depressa : De Verneuil, Geol. Russ, and the Ural, 1845, Yol. ii, pa. 234, pi. 15, f. 7. 
Leptcena tenuistriata : Hall, Palseontology of New-York, Yol. i, p. 108. 
Leptcena depressa : Hall, Palseontology of New-York, 1852, Yol. ii, p.257. 
Strophomena rhomboidalis : Davidson, Intr. Nat. Hist. Brachiopoda. 
«• << ; Ib., Monograph of the British Carboniferous Brachiopoda, p. 119. 1860. 
Strophomena rugosa* : Hall, Palseontology of New-York, Yol.iii, p. 195. 1859. 
The shell is more or less semielliptical or subquadrate, varying greatly 
in its proportions of length and breadth : hinge-line straight; car¬ 
dinal extremities sometimes rounded, sometimes acute and slightly 
produced. The valves are geniculated, and the proportions of the flat¬ 
tened part or disc and the recurved part of the shell are very variable, 
insomuch that the geniculation is sometimes little more than one of the 
strong concentric wrinkles. 
The surface of the flattened portion is marked by concentric (and 
sometimes interrupted) wrinkles, which, following the curve of the 
outline, are bent outwards, and often become obsolete on the cardinal 
angles. These concentric wrinkles are very variable in number, being 
from six to fifteen or sixteen upon specimens from the same rock. The 
entire surface is covered by radiating threadlike striae. 
In young specimens there is usually a round foramen in the apex of 
the dorsal valve, which becomes closed at a later period. The triangular 
foramen of the ventral area is partially closed by a deltidium and the 
apex of the ventral valve. 
This species is not of frequent occurrence in the Schoharie grit, but is found 
everywhere in the Corniferous limestone. The principal varieties are illustrated in 
figures 16, 17 & 18 of Plate xii, the two latter being essentially casts of the 
interior. In all the collections made in New-York, we have no specimens of this 
species from the Hamilton or Chemung groups. 
* I adopted the name S. rugosa in the third volume of the Palseontology, recognizing it as the typical 
species of the genus, and thus named by Rafinesque. The name of Wahlenberg has precedence in 
time, and will include those lower Silurian forms described as Strophomena or Leptcena tenuistriata. 
