Tertiary.) PALAONTOLOGY OF VICTORIA. [ Echinodermata. 
Description.—Subpentagonal or nearly round. 13 to 15 tubercles near margin 
above of several large and moderate sized specimens in a space of 2 lines; 9 to 
10 in same space below; very large specimens, 12 above, 6 below: 82 to 86 pores 
in each row of the ambulacral petals. Proportions :— 
ReEFERENCE.—Laube Sitzungsberichte d. Kaiserlichen Akademie d. Wissen- 
schaften zu Wien, 1869, p. 190, t. ?, fig. 3. 
This is a very variable species in form, in the strength of the 
ambulacral furrows, in the depth or distinctness of the notches in 
the margin where they pass over, and the degree of curvature or 
straightness of the posterior pair of ambulacral furrows, and the 
prominence of the posterior interambulacrum at the margin, and 
I do not find any coincidence between the variations; nor do I 
think Dr. Laube’s observation, “Die jiingsten Exemplare sind 
fast kreisrund, mit kaum angedeutetem Rostrum und unmerklichen 
Randkerben, auch du Ambulacralfurchen sind kaum wahrnehmbar, 
erst im mittleren Alter werden letztere deutlicher und das Rostrum 
tritt mehr und mehr hervor, bis es sich scharf und deutlich abhebt,” 
borne out by the very numerous specimens I have examined, as 
some very small ones are of the longest proportions, and have the 
most projecting posterior interambulacrum (Rostrum of Laube) of 
any I have seen, and the largest specimens have the least indenta- 
tion of the margin at the passage of the ambulacral furrows and 
least projection of the hinder part. Most of the nearly circular 
examples are, however, small, while small and large show the slight 
elongation of the more pentagonal forms. Towards the margin of 
large specimens the ridges between the granules on the under side 
show a tendency to diverge in oblique, feather-like lines from the 
ambulacral furrows; but this also is very variable and often not 
recognizable, although occasionally seen in all the above noted 
varieties. 
DEC, VI. [ 41 ] F 
