96 PALJEONTOLOOY OP NEW-YORK. 



133. 7. LINGULA QUADRATA. 



Pu XXX. Figs. 4 a, b, e. 



Crania quadrata. Kichwau), 1829, Zool. spccialis, Vol. i. pag. 273, pi. 4, fig. 2. 

 JJngula quadrala. F.iCHW. 184U, Sil. Syst. in Rsthland, p. 1G4. 



— — Id. 1840, Urwclt Russlands, heft 1, p. 15. 



— — Id. 1842, Ibid, heft 11, p. 58. 



— — MuBCHisoN and Verheuil, GcoI. Russia and tlie Ural Mountains, Vol. ii. pag. 292, 



pi. 1, fig. 10. 



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

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

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

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

 distinct longitudinal stria;, 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 ) ; but it is more regularly rounded at the base, and does not present the 

 squars outline which that 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 strise mark only the 

 central part of the shell, and are 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 

 species. 



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



radiating striffi along the centre. 

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



compression. 

 Fig. 4 e. A specimen of larger dimensions, from which 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, unassociatcd with other 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, being 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. ~ 



