128 CATALOGUE OF THE BLASTOIDEA. 



that the number of so-called species of Pentremites would be very greatly reduced if 

 they were all subjected to a critical examination which was based on the comparison 

 of a large amount of material. In one or two cases this has been, to some extent, 

 possible for us. Thus, for example, we have a striking series of forms which we 

 refer to Pentremites Godoni (PL II. figs. 1-7), among them being Pentremites abbre- 

 viate, Hambach (fig. 4). Pentremites symmetricus, Hall, seems in like manner to 

 link together several varieties of Say's older species P. jiyrtformis (PL II. figs. 24- 

 30) ; while, following the lead of Prof. R. P. Whitfield, we cannot regard Hall's P. 

 conoideus and P. Koninckanus as distinct species (PL II. figs. 16-23). On the same 

 plate are shown two very dissimilar forms of P. elongatus (figs. 14, 15) and four 

 varieties of Granatocrinus Norwoodi which pass very gradually into one another (figs. 

 32-35). A similar variation occurs in the British G, ellipticus (PI. VIII. figs. 

 16-19 ; PL X. fig. 16). 



From these few examples we may not unfairly conclude that a revision by com- 

 petent hands of the host of different species of Pentremites which have been described 

 in America would reduce a great proportion of them to the rank of synonyms. It is 

 equally probable that a similar abundance of material would render the same course 

 necessary in the case of the European species of Pentremitidea described by ourselves. 



