190 IOWA STUDIES IN NATURAL HISTORY 
sandstone cliffs which constitute the ‘‘Pillars’’ there is an al- 
most level bed of hard rock over which the breakers surge at high 
tide and occasionally even at low tide. This rocky ledge has a 
number of cracks or fissures, and in these Echinometra fastens 
itself firmly to withstand the sweep of the waves. It is sur- 
prising how tightly these urchins wedge themselves and how 
hard it is to dislodge them. The species is quite variable in 
color and the actinal surfaces are often brilliant red, almost 
crimson, and their spines dull terracotta. Generally, however, 
the spines are purplish black, or sometimes dark green. They 
seem to prefer shade to sunlight and are often found under 
stones, where they share quarters with the equally abundant 
serpent star, Ophiocoma echinata. Cidaris tribuloides is an- 
other species found here but it appears to be rare; there is 
but a single specimen in our collection. 
We were much interested in two species of spatangoids which 
are common here, although one must know where to find them. 
After we learned their ways and manners, we secured a good 
series of each. They were most abundant at the place which we 
called Rocky Point, opposite Fort Barclay. The ground here is 
strewn with waterworn rocks, many of them quite flat. An area 
was stripped of these rocks and the sand beneath them exposed. 
Then with our hands we dug down six to ten inches in the sand 
and found petalostichans singly or in small groups of three to 
five. We never found living specimens on the surface of the 
sand nor even just beneath the surface, but always at the depth 
mentioned. These flats are covered with water at high tide, 
but even when so covered we never saw these curious Echini, 
although we collected there several times when the tide was in. 
The question obtrudes itself,—on what do these creatures 
feed? One would not expect to find much nutriment under a 
layer of six to ten inches of almost pure sand, nor would he 
expect to find organic matter in any quantity under an effective 
sand-filter such as this. In order to answer this question, the 
writer has examined the contents of the intestinal tract of some 
of these spatangoids and finds it filled with what looks like 
pure sand with broken bits of shell, coral, sea urchin spines, ete. 
A closer examination, however, discloses a number of Foramin- 
ifera, which, from their fresh appearance, were alive when de- 
