94 
B. NATURAL HISTORY. 
Pictet has admitted this genus and made it the type of a tribe of 
sponges (Paleont. IV. r p. 548), while McCoy indentifies it with Cau- 
nopora of Phillips. 
In 1851 Prof. McCoy investigated Stromatoporce, and controverted, 
the general impression that they are sponges, since the whole mass, 
being composed of rigid, though vesicular, curved plates, would be in¬ 
capable of those systolic and diastolic motions essential to the life of a 
sponge. On the other hand, he detected in the intercellular structure 
of Palceopora , Fistulipora, etc., something analogous to the vesicular 
structure of Stromatopora, and thought he discovered, also, some faint 
indications of the existence of individual polyp cells. He accounted 
for the absence of cell-walls by the supposed exserted position of the 
polyp, as in Goniopora. He accordingly places Stromatopora in the 
Tubiporidce , near Fistulipora (Brit. Pal. Foss., p. 12). He regards 
Caunopora as a sub-genus of Stromatopora. 
In 1862 Mr. Billings described a second species — S. compacta — 
from the Black River limestone (Paleozoic Foss., p. 55), which differs 
from S. rugosa as S. striatella does from S. concentrica. Mr. Billings 
first ranged these organisms under Amorphozoa, but from later exam¬ 
inations he states that he was led to regard them as corals allied to 
Fistulipora (lb., p. 213). 
It may be further stated that Geinitz places a portion of the Stro¬ 
matoporce under Madrepora (Yersteinerungs-kunde, p. 580), and 
others under Nullipora (lb., p. 583) ; Agassiz places them under Mil- 
leporina (Nomenclator Zool.) ; Bronn, under Bryozoa (Index, Pal. II., 
p. 1203) ; Pictet, under Spongiaires (Paleont. iv., p. 556) ; while 
Dana, in one instance, ranges Stromatopora under Bryozoa (Man. 
Geol., p. 191), and in another, under Radiates (lb., p. 240). 
I now proceed to give the results of my own observations upon the 
four species discovered in the Hamilton group of Michigan and Ohio, 
and recently described in my report on the u Grand Traverse Region,” 
pp. 90-1. 
Stromatopora pustulifera is a species which occurs in large, spheroi¬ 
dal, ovoid, or elongate masses, composed of arching, transverse, con¬ 
centric layers formed of laminae of coralline substance, separated by a 
net-work of minute passages, which, at intervals, coalesce and turn 
upwards through the bed, radiating and ramifying again on its upper 
side. The places where the beds are thus traversed are raised, on the 
