110 
Triassic Echinoderms of Bakony. 
matic sense of «genotype», and since Pedina Etlieridgei was one of the three 
species specially mentioned by Wright (Aug. 1855, Ann. Mag. Nat. Hist. ser. 
2, XVI, p. 95) as having first suggested to him the establishment of the 
genus, the action of Lambert was justified and cannot now be annulled. 1 
Both species fortunately fall into Wright’s Section I. 
The genotype of Diademopsis appears to have been first fixed by 
Coti'eau (1884, Pal. franc. jurass. Echin. X, 2, p. 439) as Diadema seriale 
Ag. in Leymerie ; and this is universally accepted. The species first mentioned 
by Desor was Hemicidaris buccalis Ag. 
Comparison of the diagnoses given by Lambert shows the following 
points of difference between the two genera. 
Diademopsis 
Hemipedina 
1 . 
Form of fest 
subrotular or subconical 
rotular 
2 
Peristome 
subdecagonal 
subcircular 
3. 
Interambulacral main 
tubercles 
eccentric adambulacral 
central usually 
4. 
Secondary tubercles 
present but thinning out 
above 
represented only by ser- 
ies of mamelonate gran¬ 
ules 
5. 
Intermediate granules 
numerous, subequal, close 
set 
almost always unequai and 
irregulär 
It is on points 3, 4, and 5 that Lambert lays special stress, and rightly 
so, for it is quite certain that points 1 and 2 are far from being of universal 
application Point 3 is not in itself of great importance, nor can Lambert 
himself regard it as universal, since he describes Diademopsis aequituberculata 
with main interambulacral tubercles «s’elevant au centre des plaques», and 
admits that they are not always central in Hemipedina. The character in any 
1 The systematists who are now endeavouring to establish a rule that the first species 
referred to a genus by its founder is to be the genotype would deny this Statement, since 
H. Etheridgei was not the first. This rule is supposed to leave no room for doubt. Nevertheless 
in the present instance it is not clear which species is to be regarded as the first. The first species 
mentioned and described after the establishment of the genus is H. Bechei (p. 96); but in an 
introductory paragraph (p. 95) three species are mentioned as having suggested the establish¬ 
ment of a new genus, and of those species the first named is goniopygus perforatus. 
In Science for June 21, 1907, I have pointed out the difficulty of applying this rule to 
the writings of palaeontologists, who so frequently introduce their species in stratigraphical 
Order, with the usual consequence that the first mentioned is the least characteristic and the 
most obscure «.Cidaris Bechei » is a case in point: probably it is what we now term Diadem¬ 
opsis, and its adoption as genotype would still further darken a problem already obscurc 
enough. The selection of Goniopygus perforatus would not be so harmful, but the rule in 
question does not seem intended to apply to any species that a writer may casually mention 
in his preliminary remarks, unless he at the same time refers it to bis genus. Goniopygus per¬ 
foratus was not referred to Hemipedina tili p. 98. 
