39 
of any Salenid. A. Agassiz (,,Blake" Echini, p. 18) gives some 
information of the apical system in the young Sa/enia varispina 
of 1,5 mm diameter; it is stated to be at that size already 
essentially as in the grown specimens; ,,the suranal plate is at 
first quite small, a narrow plate on the side of the anal system 
opposite the nearest ocular plate. It appears to gain in size at 
the edges adjoining the genital plates". The first appearance of 
the suranal plate has, however, not been observed, the specimen being 
probably too old already (— the figure, Pl. VI, 1., does not give 
the apical system sufficiently detailed; the suranal plate is not to be 
distinguished in it —). The anal system is distinetly pentagonal 
and covered by eight large, triangular plates with rounded tips... 
In the young Sa/enia miliaris there are five larger and some small 
plates along the edge of the anal area. Upon this evidence it 
seems somewhat rash to conclude that ,,it appears that the anal 
system of Salenia, as of Cidaris, was 
originally covered by five plates" (A. 
Ågaåassiz. Panamie Deep Sea Echini. 
p. 36). 
While thus the embryology does 
not as yet afford the knowledge wanted 
of the development of the remarkable 
suranal plate of the Salenids, palæ- 
ontology seems to have shown us the Fig. 4. Apical system of Acro- 
way in which it has originated. In  salenia angularis (after De 
several specie é - 
Betiae: of.409- 8ybne dcrora The sapene pores are met indicated 
lenia, there is not one single large in the original figure, At the mark 
: the figure Ra been slightly restored. 
suranal plate, but several of diffe- 
rent size, so arranged as to diminish in size towards the peri- 
proct, as shown in the fig. 4, representing the apical system 
of a specimen of Acrosalenia angularis (Ag.) Desor”). It is here 
scarcely possible to distinguish between the ,,suranal” plate and 
1) From P, de Loriol. Premier Supplément å V'Échinologie helvétique. 
Mém. Soc. Pal. Suisse. XII. 1885. Pl. I. Fig. 4 
