244 APPENDIX TO THE SUPPLEMENTS TO 



Greensand fossils. Among the specimens is an example of T. lyra, measuring 2 inches 

 7 lines in length by 1 inch in breadth and depth. It is the largest specimen of the 

 species that has hitherto come under my notice. 



3. Terebratulina gracilis, Scldotheim. Dav., Cret. Mon., PL II, figs. 13, 14 (not 



15, 16, 17). 



When describing this species at p. 38 of my Cret. Monograph I placed Terebratula 

 rigida, Sow. (' Min. Con.,' tab. dxxxvi, fig. 2), among the supposed synonyms of 

 Schlotheim's species. Subsequently, as stated at p. 31 of my ' Cretaceous Supplement,' 

 Dr. Schloenbach insisted that the shell to which Sowerby had given the name of Tere- 

 bratula rigida was specifically distinct from T. gracilis, and he referred the small Tere- 

 bratulina, which is so abundant in the Cambridge Greensand, to Sowerby's T. rigida. 



Sowerby describes his T. rigida as " orbicular, plaited ; plaits granulated, increasing 

 towards the margin ; lesser valve nearly fiat, the outer convex with a small beak," and 

 adds, " a well-defined species, with an even front and small circular opening in the beak. 

 Only one specimen of this little shell has come within my observation, it was found in 

 the Chalk near Norwich." The Cambridge Upper-Green sand shell has never to my 

 knowledge been met with in the Norwich Chalk. 



In shape and dimensions, as well as in stratigraphical position, Sowerby's T. rigida 

 in no way resembles the little, sometimes so named, Terebratulina that occurs in 

 such great abundance in the Upper Greensand near Cambridge. The T. rigida of 

 Sowerby, from the Chalk of Norwich, seems to be a rare shell, as it has never come under 

 my notice ; and its figure is oval or orbicular, while the Cambridge shell is broadly 

 triangular, and had better have a separate name. 



In the Appendix to W. H. Penning and Jukes-Brown's 'Memoir on the Geology of 

 the Neighbourhood of Cambridge ' (' Memoirs of the Geol. Survey),' p. 147, pis. 13 and 

 14, 1S81, Mr. R. Etheridge describes two specimens from the Middle Chalk and from 

 the Totternhoe stone of Cherry Hinton and Burn el, near Cambridge, by the varietal names 

 of Terebratulina gracilis, var. lata, and Terebratulina gracilis, var. nodtdosa, but I am 

 not quite satisfied that either are strictly speaking varieties of Schlotheim's true 

 Terebratulina gracilis. More specimens will have to be examined before the question 

 mooted can be solved. 



