40 
the other anal plates, which leads to the conclusion that the ,,sur- 
anal" plate of Salenia is only one of the anal plates which has 
been specially developed on account of the anal opening having 
moved to the posterior edge of the anal area, and even encroached 
upon the posterior genital plate, tending thus towards becoming 
exocyelic. This suggestion is very 
much strengthened through the ob- 
servations of Lambert on the genus 
Palæopedina"). In this genus the 
periproct is ,rejeté en arriére par 
une suranale plus ou moins persi- 
stante" (Fig. 5). In P. globulus (A2.) 
»le plus souvent la position de la 
Fig. 5. Apical system of Pa- sSuranale est nettement indiquée par 
læopedina globulus (Ag.). les contours antérieurement anguleux 
Slightly restored at the mark. 
(From Lambert). du périprocte; cependant chez certains 
individus la suranale a été moins 
développée et elle s'est pour ainsi dire confondue avec les plaques 
anales dans le cadre irrégulidrement circulaire du périprocte. Il 
semble done qu'å V'époque lointaine de VHettangien la suranale plus 
variable n'avait encore acquis la fixité et importance qu'elle devait 
plus tard atteindre dans les Acrosaléniens et les Saléniens". (Op. 
cit. p. 26—27). 
Bather (Triassic Echinoderms of Bakony. 1909, p. 106) 
modifies this view in so far as he is not inclined to agree that 
Palæopedina has ,,a form of apex in which the more or less pro- 
longed persistence of the central disc has shifted the periproct to 
the rear". ,,Is it not nearer the truth to say that the passage 
of the periproct to the rear has involved partial resorption of the 
posterior genital, wlile leaving a space to be filled by the increase 
in size of a periproctal or anal plate, which comes into contact 
with the growing anterior genitals and so produces angles in the 
11 J. Lambert. Étude sur quelques Échinides de VInfra-Lias et du 
Lias. Bull. Soc. sc. hist. et nat. de "Yonne. 1899, p. 22. 
