64 IOWA STUDIES IN NATURAL HISTORY 
respire without being immersed in water. From such a group 
it is not at all remarkable that an air-breathing form such as 
Periophthalmus has been developed. 
In his work ‘‘Fishes’’ Jordan says, ‘‘In some fishes the eye is 
raised on a short fleshy stalk and can be moved about at the will 
of the fish. It is said that the vision of the pond-skipper, Peri- 
ophthalmus, when hunting insects on the mud flats of ss or 
India, is equal to that of a frog.’’ 
THE CRUSTACEA 
Most of the forms secured were well known shallow water and 
reef dwellers and members of widely distributed genera, but they 
are always interesting on account of their marvelous adaptation 
to environment in form and color. Like the insects on land the 
crustacea represent a highly successful type of animal and, there- 
fore, a highly adaptive one. They lurk in the crannies of the 
rocky flats and retreat into the cavities of the masses of coral rock 
that dot the surface. They are hidden in the fringes of alge and 
other aquatic plants that line the edges of the tide pools and hide 
in the forkings of branched coral heads and alecyonarians. In- 
deed, they are nearly ubiquitous but usually not at all obtrusive, 
their retiring disposition being aided by an amazing ability in the 
way of camouflage, an art at which they were adepts ages before 
humanity discovered its use. Our Fiji boy, Esile, was adept at 
catching crabs and many of our specimens are due to his keen 
eyes and agility, as well as to his patience in breaking off chunks 
of coral rock in order to lay open the retreat of their crab popu- 
lation. 
The writer is indebted to Dr. Mary J. Rathbun, of the United 
States National Museum, for the identification of the brachyuran 
crabs mentioned in this brief account of the reef forms, and to 
Dr. Waldo Schmitt for that of the few macruran forms mentioned. 
A very smooth-shelled form, Carpilius convexa, has a shiny, 
polished carapace without grooves or lateral spines, but it is very 
finely punctate. It is creamy white in color with curious scarlet 
blotches, often amceboid in form. There is a central conspicuous 
blotch with two plainly marked, eye-like dots of whitish. 
Another form of erab found is Zozimus eneus, brick red on the 
dorsal surface which is strongly carunculated, like a cobblestone 
pavement. The chele have a tubereculate base and smooth olive 
greenish fingers. 
