'JornlJ 11)11 III F. f(>fhrsi\ ra r. oc.ciiJcntnl'is. — G'n'ty. 187 
aminedjthe initial c-orallite retain? a periplicral position. This 
peculiarity in the development of F. siiiniiienis is illustrated 
on plate viir, figures 6-15. 
Favorites conlriis Hall. 
Only three specimens have been secured which atlord any 
evidence as to the earlier stag-es in the development of this 
species. The}' were obtained from the Delthyris Sluily lime- 
stone of the Lower Helderberg group in Albany count}', New 
York. Figures 17, 1(S and 19 of plate viii represent the lower 
or epithecal surface of these specimens, which seem to show 
the initial cell of the corallum, together with tlu- cells next 
produced. 
The initial cell may be determined not alone by its larger 
size, for that character proves to be sometimes misleading 
when employed as a sole criterion for estimating the relative 
ages of corallites, but also b}' the shape of the theca. Where 
the corallites are all of the same age, or all mature, mutual 
pressure causes them to yield equall}' from their naturally 
cjdindrical form, one not more than another. When different 
ages are represented, crowding causes the younger cells to be 
more distorted than those older. Conseciuently, in a section 
taken across the corallum at a point before the seectndar}' cells 
had reached maturity it will ai)pear that the initial cell is 
<'omparativel3' round, but the four secondary cells, while 
rounded on the outer side, are laterally compressed, and abut 
squarely on the initial cell. A third consideration to be en- 
tertained in orienting young coh)nies, in default of a better 
way, is that of symmetry, which appears to be a constant fac- 
tor in the development of coralla. Thus, when tiie character 
of the material does not permit of determining the initial cell 
and the relative ages of other cells by observing the point at 
which each makes its appearance, these essential facts can be 
ascertained with a fair amount of accuracy' in other ways. 
No examples of Faroxitcs romoi.s have been obtained which 
represent only the younger periods of growth. Specimens, as 
usually found, are unattached, but in each case <»n the under 
surface a group of cells occupying a central and apical posi- 
tion are broken. These cells represent the cementing portion 
of the corallum, broken when the latter was detached, and in- 
dicate the number and position oi' the primitive corallites. 
