94 PALEONTOLOGY OF NEW-YORK. 



130. 4. LINGULA ATTENUATA1 



Pl. XXX. Figs. 1 a, *. 



Compare Lingula attenuala. Sowerby in Sil. Researches, pag. 641, pl. 22, fig. 13. 

 Also LinguLa acuminata, page 9 of this Report. > 



General form ovate-acute, attenuated towards the apex ; sides nearly straight ; front 

 rounded ; surface depressed, marked by concentric lines which are crossed by obscure 

 radiating striae. 



This description corresponds essentially with that of Sowerby, except that our shell is 

 never smooth. The concentric lines are more or less strongly visible in all our specimens. 

 The' sides are straighter, and the shell more attenuated towards the apex, than in any other 

 species which we have in this rock : it varies in form, however, to a considerable degree, 

 as will be seen on comparing different sjiecimens of the same species. 



Fig. 1 a, is the largest individual of this species yet seen. 

 Fig. 1 b. A specimen of the ordinary size. 



It should be observed by the student, that the proportional strength of the concentric and 

 radiating lines on the Lingula are influenced by the exfoliation of the shell which takes 

 place in many of them. In some cases the concentric lines are partially or entirely 

 obliterated by this process. 



In figs. 1 fl and b, the radiating stria; are visible, from a partial exfoliation of the shell. 



Position and localily. This species occurs in greater nmnbers aliout midway from the base 

 to the top of the Trenton limestone, and is often met with in other parts of the rock. At 

 Middleville, which is the best locality for all the species of the genus, this one is found 

 about fifty or sixty feet aboYe the Birdseye limestone. It is also found at Trenton Falls, 

 Jacksonburgh, Lowville, Watertown, and other places. The usual associates of the Lingula 

 are the Conularia, Leptana allernata, and sometimes the small corals, as Sticfopora, fyc. 



The species found in the Calciferous sandstone is far more attenuated than any which we 

 find in the Trenton limestone, and is perhaps tpiite distinct from the L. attcnuata of the 

 Llandeilo flags, as it is, apparently, from the present species. That figured by Murchison 

 is intermediate in form between the two, being less attenuated than the one in the Calci- 

 ferous sandstone, and more attenuated than the one imder consideration. If the LiNGUL.ff:, 

 like other genera of the Braciiiopoda, were influenced in form by the nature of the sediment 

 deposited, or the ocean bed on which they lived, then the same species may present the 

 extremes of form here noticed. 



