The Pluteus of Laganum sp. 133 
Soa ES = 
CSOD ie oh 
ro) 
\ 
C DH 
(Ke BESGO 
Be Sictne 
OS 
“Ao Sy 
ROIs 
uereal 
16 
Figs. 4 to 15.—Series showing development of plates and spines of the permanent skeleton of 
Laganum. Figs. 4, 5, 12 to 15 viewed from ventral surface. 6 to 11, from dorsal surface. 
b}, b?, b’, branches from each of the six primary rays, which by uniting with one another and 
with the wheel-like structure at their exterior ends, form 6 radiating plates in the base of the 
spines; c, 6 branches of the primary rods which form the cup-like basal portion of the spine; 
p, plate; ps, portion forming small secondary plate which lies between the primary one and 
the spine; w, portion forming wheel-like base of the spine. Figs. 4-10, X466. Figs. 13-15, 
350. 
Fic. 16.—Permanent plates and spines viewed from the oral surface, showing their characteristic 
arrangement around the anlage of the adult mouth, m. a. p., adult plate; a.s., adult spine. 
X 265. 
