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Diadema, which he rejects, establishing instead of it a new name 
Centrechinus (— and accordingly a new order-name, Centrechinoida, 
instead of the well-known Diadematoida —). His reason for doing 
this is that the name Diadema is preoccupied for a Cirripedian, 
while also a genus of butterflies and one of Gastropods have later 
on received the same name. He therefore thinks it better to drop 
this name altogether from Echinology. 
This seems to me very injudicious. If the name Diadema 
stood alone in Echinology, there would be no very great harm 
done by this course. But what about all the names composed of 
.….… diadema. There is Eodiadema, Mesodiadema, Pseudodiadema, 
Hemidiadema, Hypodiadema, Diademopsis etc. etc. — all names, 
which can under no condition be altered, but the name Diadema 
itself, known by any zoologist and palæontologist and used in all 
the echinological literature of the last century, must not be used, 
because the name was given in 1817 to a Cirripedian! — and for 
which it can even not be used, being a synonym only of the well 
known name Coronula Lmk. (from 1802)! Furthermore the name 
Diadema was in fact long before this time used for a sea-urchin, 
which belongs, in any case, to the family Diadematidæ, even if it is 
perhaps not the same as the genus now called Diadema, viz. by 
Schynvoet (Thesaurus imaginum Piscium testaceorum 1711)!). 
It is, of course, to be regretted that the name cannot be used for 
the butterflies and snails which have been thus designated; but 
they cannot possibly be taken into consideration here, having got 
that name after it was in use for the sea-urchins. In these cases, 
however, the difficulty can be quite simply avoided by merely 
Changing the name …a little, e. g. into Diademéa, Diødema, Diade- 
mella or the like; by that way the continuity is easily kept. For 
the Echinoid name such change cannot be adopted, because of the 
numerous combinations with -diadema. Here is a case, where the 
name should be protected; to change the name Diadema is against 
7) I have not seen this work myself. 
