0 * eras so lame Hat a 
- 19 - 
and presents eve ry variety of siliceous f oa si libation, from that 
characterized hy silicif ication of the sclerenchyma and in- 
filtration of the interspaces hy granular carbonate of lime, to 
that where all is siliceous and capable of polish. Destructive 
silicif ication almost invariably exists in a greater or less de- 
gree; and as the sections preserved were made, as a rule, for 
ornament fir amusement, I have seldom seen accurately transverse 
and longitudinal views of the corallites. 
All the specimens, with the specific peculiarities mentioned, 
may be ranged in seven groups; that which contains the detailed 
characters in their greatest intensity, generally, may be 
considered the typical form# 
a. Astraea crassolamellata, typical form, PI, XIII, figs, la-lc , 
Corallum large, irregularly convex above, Corallites tall, 
large, crowded here and there, but not so much so higher up or at 
the surface, Calices circular, but more or less elliptical when 
on an irregularity of the surface; very large, and separated from 
each other by well-marked, furrow- shaped, polygonal tracts; tracts 
