153 



TEREBRATULA acuminata. 

 TAB. CCCCXCV. 



var. sulcata, (fig. 1.) var. plicata. (Jig. 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 Encyclopedie 

 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. 



