94 PALEONTOLOGY OF NEW-YORK. 
130. 4. LINGULA ATTENUATA? 
Pu. XXX. Figs. 1 a, b. 
Compare Lingula attenuata. Sowrrsy 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 strie. 
This description corresponds essentially with that of Sowrrzy, 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 specimens 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 Lineura 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. 1a and 4, the radiating strie are visible, from a partial exfoliation of the shell. 
Position and locality. This species occurs in greater numbers about 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 above 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, Leptena alternata, and sometimes the small corals, as Stictopora, &c. 
The species found in the Calciferous sandstone is far more attenuated than any which we 
find in the Trenton limestone, and is perhaps quite distinct from the L. attenuata of the 
Llandeilo flags, as it is, apparently, from the present species. That figured by Murcuison 
is intermediate in form between the two, being less attenuated than the one in the Calci- 
ferous sandstone, and more attenuated than the one under consideration. If the LineuLz, 
like other genera of the Bracuropopa, 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. 
