24 PALJEONTOLOGY OF NEW YORK. 



The shell-substance in Lingulops is exceedingly tenuous and not usually 

 resolvable into layers. The fossils are generally preserved as thin white films, 

 through which the thickened muscular area is plainly visible by its deeper 

 color. Its color alone indicates that its substance is largely if not quite cal- 

 careous, differing from Lingula in this respect, but agreeing with Lingolasma 

 and the Trimerellids. 



Genus LINGULASMA, Ulrich. 1889. 



PJ.ATE II, FIGS. 17-23. 



1889. Lingulasoia, Ulrich. American Geologist, vol. iii, No. 6, p. 383, figs. 5 a, h, c, d (p. 378). 

 Compaj-e Linffula Canadensis, Billings, 1862. Palaeozoic Fossils, vol. i, p. 114, fig. 95. 



Diagnosis. Shell sub-quadrate, linguliform, sub-equivalve ; the brachial 

 valve considerably the deeper. Beaks apical, cardinal margins gently sloping 

 to the sides. 



Interior of the pedicle-valve with a low concave platform which extends 

 over one-half the length of the shell, and is not hollowed on its anterior wall. 

 The pedicle-area has been largely enclosed within the shell, making a distinct 

 sheath or shelf, beneath which lie the apical portions of the central and lateral 

 muscular scars. Crescentic scars scarcely defined. 



The brachial valve is deep, with a high platform of about the same extent as 

 that on the other valve, sloping inward near its anterior margin and continued 

 axially into a strong septum, which reaches nearly to the front of the valve. 

 The anterior walls of the platform are broadly excavated, and close against the 

 base of the septum are holloAved out into short conical cavities. The crescent 

 is strongl}- developed and sharply pointed backward at its center. Its lateral 

 curves are broad, reaching to the edge of the platform. Directly in front of 

 its central angle lies a short, sharp, median ridge, which disappears near the 

 center of the platform. Lateral aud central muscular scars well developed. 



Type, Lingulasma Schucherti, Ulrich. 



Observations. This remarkable form serves as a most important connecting 

 link between the pala30zoic Lingulas and the Trimerellids, following, in the 



