CAMBRO-SILURIAN FOSSILS. 231 



fine, sharp, subequal, spiral striae (about thirty-five in the space 

 of one Hne on the basal whorls), crossed by a few obsolete, sig- 

 moidally arched lines of growth. Length about 8 lines, width 

 at base 3 lines, length of last whorl 2 lines, length of penul- 

 timate whorl 1^ line. 



I imagine this may be the Scotch fossil referred by Mr. Salter 

 (Quart. Geol. Journ. for August 1851) to the Upper Ludlow, 

 Turritella [Holopella) ohsoleta of Sowerby, as it has very much 

 the same size and shape ; and the distinctive spiral lineation re- 

 quires a good cross light and some care to detect*; but with these 

 and a lens of low power it may be always seen, even in the sand- 

 stone casts, and the species thus easily distinguished from that 

 of the newer rocks. The sutures are always more oblique than in 

 the H. ohsoleta. The slight inequality of size of the striae seems 

 in parts subalternate, in parts irregular. 



Common in the sandstone of Mulock quarry, Dalquorhan. 



{Col. University of Cambridge.) 



* I have since demonstrated the striation to Mr. Salter in his s})ccimen. 



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