20 PALEONTOLOGY OF NEW YORK. 



tioii.* But neither of these figures proved satisfactory to the authors, and they 

 inserted an additional figure in the text (p. 1G5). The figure which is now 

 given of this valve (Plate II, fig. 28) has been made with great care 

 from the original specimen, and is reduced from a camera drawing. 

 Though it differs in some respects from previous figures, the accuracy of 

 its details is supported by internal casts of other specimens of the same valve, 

 though none are so clearly developed as in the original specimen. Notwith- 

 standing the great value of the observations by the English authors upon the 

 structure and generic relations of this species, it must be said, that, of all the 

 illustrations which have been given of the original valve, the wood-cut referred 

 to, represents the interior features with the least accuracy. 



Both valves of Lingulops have a relatively broad cardinal area, which is 

 divided transversely into two parts, (a) a smooth, narrow, apical portion ; {b) a 

 broad inner band, along which the valves appear to have been in contact. In 

 L. Whifjieldi, this band is flattened and projects into the interior cavity of the 

 shell, like a narrow lunate shelf; on the pedicle-valve it is concentrically 

 striated, while, in L. Norwoodi and L. Granti, it is smooth, and not flat but 

 gently convex. The pedicle-groove crosses this inner area only, not encroach- 

 ing on the apical area of either valve ; in the pedicle-valve of L. Whitfieldi it is 

 sharp and narrow, in the brachial valve, broad and faint; while in the pedicle- 

 valve of X. iVorwooofz, it is very indistinct, and not discernible in the opposite 

 valve. 



Directly in front of the cardinal area, is a narrow crescentic ridge, the ante- 

 rior margin of which is deeply excavated. This ridge, which is parallel and 

 co-extensive with the cardinal area, bears a median angulation, projecting 

 backward toward the pedicle-groove. This feature is more clearly defined in 

 L. Whitfieldi than in any specimens of L. Norwoodi that we have examined, but 

 it is evident in the pedicle-valve of this species also, where it is interrupted 

 beneath the beak by a thickened area which may represent the position of the 



* The original figure was di-a\vn fi'om a natural cast to which a portion oi' the shell adhe:-ed. Davidson 

 and King's figure, being made from a gutta-percha impression, gave the inteiior markings in their natural 

 relief. 



