UPPER, OR FLINTY CHALK. 211 



serrated, and sometimes marked by several rows of plicated indentations, 

 formed by the lines of growth. 



The elevated front margin, and the numerous striae with which both 

 valves are covered, distinguish the present species from the other striated 

 terebratulae of the chalk. 



Localities. Upper, and Lower chalk, near Brighton and Lewes. 



82. Tevehvaiuhi siibplicata. Tab. xxvi. figs. 5, 6, 11. 



Transversely ovate, gibbous, nearly smooth; lower valve depressed, 

 upper valve convex ; margin serrated ; front sinuate, Vvdth three or four 

 sharp plicae ; beak slightly produced. 



This is a small species, weU characterized by its smooth surface, and 

 elevated plicated front. The young of T. plicatilis, (the only chalk tere- 

 bratula with which it can be confounded) have both valves covered with 

 minute striae. 



Like the other species of this genus, considerable variety is observable 

 in the contour of the shell, in different specimens. The pUcae are from 

 three to five in number, and extend a short distance on both valves. The 

 beak is very small. 



Locality. Upper chalk, near Lewes. 



Inoceramus. 

 This genus was formed by Mr. Sowerby for the reception of the fibrous 

 bivalves, whose fragments occur in such prodigious quantities, in almost 

 every locality of the Upper and Lower chalk. These shells were first 

 noticed by Da Costa, who describes them as being " very large hmpets, 

 which, like the concholepas, resemble the single sheU of a bivalve. They 

 are of two kinds, and more irregular than that shell ; and instead of being 

 sulcated lengthwise, are circularly wrought, in a transverse manner, with 

 very high irregular ridges, not thickly but rather thinly set. The shells 

 are very thick; one sort is high and copped; the other is broad and 

 flattish* " 



* Elements of Conchology, p. 142. 



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