Tertiary. | PALZ ONTOLOGY OF VICTORIA. [ Echinodermata. 
the tuberculation of the upper and lower surfaces is more nearly 
alike ; the diameter of the tubercles, in the fossil, is usually greater 
than the intervening flat space, but much less in the living form, in 
which the comparatively wide flat granular spaces between the 
tubercles are conspicuously different. The number of pores in the 
rows of ambulacral petals is also a marked and obvious difference 
between the living L. ¢estudinarius and the present fossil species ; 
there being thirty-six in the anterior petals, and forty in the posterior 
petals of the recent form, but only twenty-five in the anterior, and 
twenty-nine in the posterior petals in the fossil. The greatest 
difference is, however, to be found by making a horizontal section 
of the margin, where, in specimens of the same size and thickness 
of margin, the fossil has five to eight concentric rows of vertical 
calcareous pillars extending from the lower to the upper walls, 
exactly as in the recent Clypeaster subdepressus (Gray) (Ag. Rev. 
Echin., t. 13, f. 17 ; and t. 11°, figs. 3 and 4 ; and t. 11°, figs. 1 and 
2; and t. 12%, fig. 4), while the recent Echinanthus testudinarius 
has only one row round most of the margin, and no more than two 
imperfect rows on the posterior edge. The interior, except where 
the intestine winds, is crowded with the 
Ppa OT at eat very slender needle-like calcareous fila- 
(uo Qi) Bi i mentary ‘vertical extensions from the 
Vefeatel lies esclede vie, “alan 
upper and lower walls of the testa, so 
fet LEREE and lowerealla; common in the typical living species of 
Clypeaster. 
I very much doubt the wisdom of maintaining Clypeaster and 
Echinanthus as distinct genera, when the characters are so com- 
pletely united as we find them in the recent Australian Echinanthus 
festudinarius of Gray. The genus Clypeaster is supposed to be 
distinguished from Kehinanthus by the flatter lower surface, smaller 
depressed space in which the mouth is sunk, by the better defined 
ambulacral grooves on the under side, by the walls being thinner, 
single and not double as in Hehinanthus, and by the many slender 
needle-like styles rising from the lower floor, contrasting with the 
more massive columns of Hcehinanthus. The pores on the edges 
of the ambulacral plates beyond the petals, supposed to be another 
distinctive character, do not seem to exist in the Malta Clypeaster 
[ 34 ] 
