96 PALjEONTOLOGY of NEW-YORK. 



133. 7. LINGULA QUADRATA. 



Pl. XXX. Fig3. 4 a, b, c. 



Crania quadrata. Eichwald, 1S29, Zool. specialis. Vol. i. pag. 273, pl. 4, fig. 2. 

 I.ingula quaibata. Eichw. 1S40, .Sil. Syst. in Esthland, p. 104. 



_ — Id. 1S40, Urwelt Russlands, heft 1, p. 15. 



_ _ Id. 1S42, Ibid, heft 11, p. 58. 



— — MuRCHisoN and Verneuil, Geol. Russia and tlie Ural Mountains, Vol. ii. pag. 292, 



pl. 1, fig. 10. 



Eqiii valve, equilateral, broadly oval, depressed-convex ; sides nearly straight and parallel, 

 or slightly curved; extremities nearly equal in Avidth, the first broadly rounded, cardinal 

 extreniily slightly narrower and somewhat angularly sloped ; beak marginal, not prominent; 

 exterior surface of the shell marked by strong concentric stria?, and along the middle by 

 distinct longitudinal striir, which are equally visible when the outer shell is exfoliated. A 

 longitudinal depressed line marks the shell from the beak nearly half way to the base. 



This species is perhaps the largest fossil Lingula known : it is distinguished by its 

 general elliptical form and nearly parallel sides. In its dimensions it is near the Lingula 

 Lewisii ( Sowerby ) ; Init it is more regularly rounded at the base, and does not present the 

 square outline which tiiat shell has. Our largest specimen is one inch and a half in length, 

 with a width of almost an inch. 



The usual length of this shell is one inch, and its great size alone is commonly sufficient 

 to distinguish it from any other species in our strata. The longitudinal striae mark only the 

 central part of the shell, and arc equally distinct when the shell is exfoliated : this character 

 may be useful in detecting the species. 



Our shell is evidently identical with that of Russia, as cited above, both from the figure 

 and description, and from the opinion of M. de Vekneuil, who has seen the Trenton 

 sjiecies. 



Fi<^. 4 a. A specimen of the ordinary size; the shell partially exfoliated, and presenting the strong 



radiating striae along the centre. 

 Fig. 4 //. View of the edge of the sliell, with the two valves closed. It appears slightly inequivalve from 



compression. 

 Fig. 4 c. A specimen of larger dimensions, from wliich the shell is partially exfoliated. 



Position and locality. This species occurs in the central and higher part of the Trenton 

 limestone, usually in the compact dark layers, unassociated with otiier fossils. In some 

 instances, it occurs in the higher gray rock. Trenton Falls, Middleville, Turin, Lowville, 

 and other localities in New-York. It has a wide geographical range, l)oing known in Ohio 

 and Wisconsin, where its geological position is similar to that in New-York. Its occurrence 

 in several localities in Russia proves its distribution over an immense area in the palaeozoic 

 seas. 



