188 IOWA STUDIES IN NATURAL HISTORY 
It is a fine form for laboratory study and furnishes excellent ma- 
terial for research in the line of individual variation. The col- 
ors here, however, are not so vivid as we found them in the Ba- 
hamas, dark red predominating. 
Many of the sea-urchins collected were of the same species 
as were found at Barbados. The white sea urchin, Hipponde 
esculenta (or Tripneustes esculentus, according to Clark in his 
‘‘Crinoidea and Echinoidea of the Bahama Expedition’’), 1s 
found on muddy bottom in Falmouth Harbor. Dr. Clark does 
not give us any clue to his reason for abandoning the familiar 
generic name Hipponée for this form. It was used by Agassiz 
in 1872 and has become firmly established in the literature of 
the Echini. Clark cites the name TZ'ripneustes esculentus as 
used by Bell in 1879, which does not indicate a priority for that 
name. The writer believes it is preferable in the present work to 
use the names familiar to the general zoologist, even when prior- 
ity has been proven for some other name. 
This species does not seem to be in general use as food at 
Antigua. While not so abundant as at Barbados, there are 
places where it is quite common and could doubtless be secured 
in sufficient quantities to be of considerable importance in times 
of food scarcity such as are by no means unknown in Antigua. 
In the mud-flats it is almost invariably covered with eel-grass, 
small stones or shell, which seem to be placed there by the ani- 
mals themselves for purposes of concealment. Here again we 
find the two forms of this species already referred to. One 
form is entirely white, while the other appears to be black with 
white spines. The black color is due to innumerable black- 
headed pedicellarize packed in between the spines so thickly as 
to give an impression that the test itself is black. It seems that 
this is neither a sexual nor seasonal difference, both sexes being 
found in the same form and at the same time. It may be that 
we here have a kind of dichromatism among the Echini such as 
is found not infrequently among birds, e. g. the common screech- 
owl, and of which I have seen no adequate explanation. It 
hardly seems likely that two species so nearly alike would 
constantly occur in close association. They are found in very 
shallow water in Falmouth Harbor. Indeed, they are often in 
