110 
Triassic Echinoderms of Bakony. ; 
Be ae 
matic sense of «genotype», and since Pedina Etheridgei was one of the three 
species specially mentioned by Wricur (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 LamBertT was justified and cannot now be annulled. ! 
Both species fortunately fall into Wricur’s Section I. 
The genotype of Diademopsis appears to have been first fixed by 
Cotrrau (1884, Pal. franc. jurass. Echin. X, 2, p. 489) as Diadema seriale 
Ac. in Leymerie; and this is universally accepted. The species first mentioned 
by Drsor was Hemicidaris buccalis Ac. 
Comparison of the diagnoses given by Lampert shows the following 
points of difference between the two genera. 
Form of test 
Peristome 
Interambulacral main 
tubercles 
Secondary tubercles 
Intermediate granules 
Diademopsis 
subrotular or subconical 
subdecagonal 
eccentric adambulacral 
present but thinning out 
above 
numerous, subequal, close 
set 
Hemipedina 
rotular 
subcircular 
central usually 
represented only by ser- 
ies of mamelonate gran- 
ules 
almost always unequal and 
irregular 
It is on points 3, 4, and 5 that Lampert 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’élevant au centre des plaques», and 
admits that they are not always central in Hemipedina. The character in any 
! 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. Aechei (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 Bechet» 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 obscure 
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 tohis genus. Goniopygus per- 
foratus was not referred to Hemipedina till p. 98. 
