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106 IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
2. Chert, white in color, broken into angular frag- 
ments; brownish geest filling the crevices be- 
tween the pieces $4-% 
1. Dolomitic limestone, light buff to yellow, sub- 
crystalline, with nodules of chert, arranged 
more or less in layers. A few' fossils consist- 
ing of bits of brachiopod shells and small col- 
v onies of Favosites favosus and Syringopora, 
exposed 14-3 
The water in time of freshets on cutting through the coral bed 
— number three of the section — has removed the lower solid part 
in large irregular blocks and has scattered them down the gully 
for several rods. A mass roughly five feet by four feet by one foot 
and another six by two by one were the largest, seen in the float. 
Headward the gully ends at the wagon road which is along the 
north side of the northeast quarter of section six, township 85 
north, range two west. The coral bed continues on but its extent 
in the upstream direction can not be determined. In the sides of 
the gully the coral is exposed for approximately fifty feet, its 
thickness, as given above, is fairly uniform and the width of the 
gully at the level of the coral bed will average about ten 
feet. This makes the cubical content of the part removed, 
SO'xlO'xl^', or 625 cubic feet. 
The slender stems of the corallites, averaging about five milli- 
meters in diameter, lie in a semi-prostrate position making an 
angle of fifteen to twenty degrees with the horizontal. In general 
the stems radiate as if from a center near the head of the gully 
but in places, for a distance of a foot or more, they lie at various 
angles even up to a right angle to this direction ; in a block one 
foot thick variations in direction of growth may be observed at 
different levels but the general direction is as indicated above. 
Since coralla of this type of anthozoans are, as a rule, more or 
less circular and their corallites radiate away from a common 
center we would seem to have here a spreading corallum of fairly 
uniform thickness and with a radius of at least fifty feet! This 
would give us a colony with a volume, u r 2 h, or 3.1416x50 2 xl34, 
or over 9800 cubic feet, and with a surface area of 7854 square 
feet. Lest the assumption as to the radius of the colony appear 
too generous we may take the fifty feet observed in the gully as 
its diameter and thus disregard the evidence offered by the 
general radial position of the corallites ; still this dimension would 
