41 
front border of the periproct? The half formed suranal is not 
the relic of a pre-existing «disque central» : at least I know of no 
structure in pre-existing Echinoid genera to whick such a term has 
been or could be applied. If it has any significance it is as 
showing the mode of origin of the 'permanent and fuily formed 
sur-anal hi the Saleniidae 1 ). In itself it can kardly be the fore- 
runner of the Saleniid sur-anal“, since Palæopedina cannot be 
regarded as an ancestor of the Salenids. I fully agree with Dr. Bath er 
in this view of the origin of the suranal plate of the Salenids. 
To regard the suranal plate as a case of atavism — „one of those 
cases of the sudden reappearance of an ancient structural feature 
after a long period of time u —as suggested by Agassiz („Blake“ 
Echini p. 16) there is nothing to support. Likewise there are no 
facts to support a supposition that the suranal plate may have 
originated through a fusion of the anal plates, as seems to be 
expressed by the Sarasins wken saying: 
Saleniden haben also die Tendenz zu ver- 
scbmelzen“ (Uber die Anatoraie der Eckino- 
thuriden und die Phylogenie der Echino- 
dermen. Ergebn. naturw. Forschungen auf 
Ceylon. I. 1887—88, p. 150). 
Some words may here be said of the 
genus Gauthieria Lambert. The remar¬ 
kable apical system of this genus (Fig. 6) 
is described by Lambert 2 ) (Op. cit. p. 4) 
as consisting of «1° Une plaque centrale 
hexagonale; 2° Trois plaques secondaires 
antérieures, hexagonales; 3° Des plaques 
nombre probable de huit» — besides, of course, the usual number 
of genital and ocular plates. Lambert lays great stress on this 
central plate. «Cette plaque centrale hexagonale tout a fait par- 
0 The italics are mine. 
2 ) J. Lambert. Note sur un nouveau genre d’Echinide de la Craie 
de l’Yonne. Buli. Soc. sci. hist. & nat. de l’Yonne. 1888. 
„Die Analplatten der 
Fig. 6. Apical system of 
Gauthieria radiata. 
(From Lambert). 
suranales variées, au 
