No. 440.] CORRESPONDENCE. 57 5 



occurring in the identical formation, and exhibiting similar tex- 

 ture or surface markings. We wonder how many would be con- 

 verted to this belief until a Trilobite had first been discovered 

 with the actual members preserved in situ ? 



In precisely the same way we must reject Professor Patten's 

 theoretical association of parts as erroneous, and deny that forms 

 like Tremataspis, Cyathaspis, Cephalaspis, Tolypelepis, etc., 

 possessed paired segmented appendages until at least one single 

 individual shall have come to light having the postulated organs 



