TOXASTER COMPLANATUS. 329 
ToxasTeR (Spatangus) compLtanatus. Lign. 108.—In 
this form of Spatangus (constituting the genus Toxaster 
ATO HmMM EN 
in 
‘= , mice 
lal \ bldg aH 
ui wii 
nn an \ 
Lien. 108. TOXASTER COMPLANATUS. 
Greensand. Switzerland. 
Fig. 1.—Frofiie. 
2.—View of the summit, showing the Vent at the side; e. 
3.—View of the base, displaying the situation of the mouth, 
and the union of the five ambulacra; their pores are not 
introduced in figs. 2 and 3. 
a. The narrow porous divisions of the shell, termed Ambu- 
lacra. 
b. Interambulacral spaces. 
c. Aree, or spaces covered by the wide plates. 
d. The Mouth. 
e. The Vent, or Outlet. 
Agass.), the ambulacra are not depressed or furrowed, as in 
the preceding echinites, nor petaloid (/eaf-shaped), as in 
those which M. Agassiz denominates true Spatangi, but con- 
verge to a point on the summit, as is shown in fig. 2; the 
external rows of pores are elongated horizontally, and form 
