x PEEFACE. 



American fellow-workerSj in the hope that one of them will undertake a critical 

 revision of the American species of Blastoidea. We would further express the hope, 

 however, for the sake of our successors, that this work will not be attempted by any 

 mere collector, however zealous, and no matter how many thousand specimens his 

 cabinet may contain, but by a trained palaeontologist who is acquainted with the 

 principles of morphology in general, and with that of the Eehinoderms in particular. 

 For we feel very strongly that unless systematic Palaeontology is based upon Morpho- 

 logical principles its results are not likely to have any permanent value ; and we 

 could wish that some of Roemer's successors had realized this fact as clearly as he 

 did himself. 



R. ETHERIDGE, Jun. 



P. HERBERT CARPENTER. 



Department op Geology, British Museum 



(Natural History), 



June. Ism;. 



