54 
too advanced for showing the first formation of the apical system, 
do not leave any doubt that also in these forms a central or sur- 
anal plate is not developed. It may then fairly be concluded that 
in the Amphisternata, upon the whole, there is no central or sur- 
anal plate"). Likewise it is evident that there is no indication 
of the periproct being originally covered by five radially placed 
anal plates (,,infrabasalia"). 
One group is still left, viz. the Uasuldilpidea Here the 
apical system shows the most interesting feature, that — in some 
forms at least (Galeropygus, Hyboclypeus, Clypeus, Pyrina a. 0.) — 
there is one or more small plates included by 
the apical plates (Fig. 15). Lovén (Études, 
p. 82) explains this as a division of the cen- 
tral plate and establishes as a general rule 
that ,,toutes les fois que le disque se trouve 
divisé, le madréporite est limité å la costale 2, 
Fig. 15. Apical tandis que, quand le disque est entier, le 
system of Galero- — madréporite s'y établit". It is certainly a 
ygus marconi Des. 
(From Lovén). much more natural explanation that the plate 
containing the madreporite is the genital 2, 
even if it is widened so much as to occupy the whole middle space 
of the apical system or even more, and the small plate (or plates) 
appearing behind the madreporite are not parts divided off from 
the central plate, but represent the central plate itself. Thus 
the Cassiduloidea have a real central plate and, indeed, 
so strikingly recall the Salenids herein, that the suggestion lies at 
hand that they are developed as a separate branch from the Sale- 
nids, being without any nearer relation to the other ,,Irregular" 
Echinoids. I Moy here also point out two other important facts 
y In the Echinoidea of the Swedish Southpolar Exped. p. 98 is men- 
tioned a specimen of Amphipneustes Koehleri, in which the madre- 
porite is abnormally divided, so that we find a separate plate in the 
middle of the apical system; there is, nonner no doubt that this is 
an abnormality, and this case cannot be taken as a proof of the 
existence of a central plate in the pantere huiee 
