153 
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TEREBRATULA acuminata. 
TAB. CCCCXCV. 
var. sulcata, {fig. 1.) var. plicata. {fig. 3.) 
Upon a comparison of several Irish and Derbyshire 
specimens of Terebratula acuminata with many similar 
to those before us, we have observed that the species is 
liable to much variation in form, but is not generally so 
blunt nor so strongly sulcated as the handsome variety 
represented in fig. 1. We are also able to confirm our 
suspicions that fig. 1 of PI. 246 of the Encyclopedic 
Methodique is undoubtedly a representation of one 
of the varieties, and has been erroneously quoted by La- 
marck as Terebratula spirifera (Spirifer cuspidatus M.C. 
120), a totally different shell. The variety with from 
3 to 5 plaits in the margin of the sinus is generally small, 
but sometimes twice as big as the figure. 
We have been induced to give figures, to show the 
near approach of these varieties to the following species. 
The specimen (fig. 1) is in the rich collection of Charles 
Stokes, Esq. : it is from the Mountain Limestone tract 
about Clitheroe in Lancashire. The other variety (fig. 3) 
is common in Ireland, and also occurs near Clitheroe. 
