480 The American Naturalist. [May, 
was very hard, igneous or metamorphic, I think, though I took no note 
of its lithologic character.”’ 
The above quotation is interesting as giving a new location for seai 
urchin excavations, although A. Agassiz has already mentioned the 
rock excavations made by the same species at Panama. 
Sea-urchin excavations near San Diego, California, have also been 
called to my attention by Dr. Cleveland and Mrs, R. S. Eigenmann, 
and an account of the same from near the Santa Barbara Islands was 
given me by a fisherman. 
A. Agassiz says: “On the coast of California the common Strongy- 
locentrotus purpuratus occurs in the same way [as in the Azores,— in 
cavities dug out of the solid rock,]; we find long tracts of the shore, 
where this sea-urchin is common, completely honey-combed and pitted 
by cavities and depressions, in which they seek shelter against the 
powerful surf continually beating against the rocks. The same species 
does not excavate in sheltered places, where sea-urchins can find pro- 
tection between the interstices of large fragments of rocks, or ledges 
more or less sheltered from the direct action of the open sea.” [Re- 
vision of the Echini, p. 706.] It would seem that these excavations 
are not uncommon to the west coast of North America, although very 
few definite localities where they occur have up to the present time 
been recorded. 
As the author desires to gather information in regard to the distribu- 
tion of sea-urchin excavations, and the extension or limitation of the 
habit among genera and species of the Echinoidea, he desires to cor- 
species of sea-urchins which make the excavation, the kind of rock 
excavated, and peculiar circumstance connected with the species, 
Boston, Mass., April gth, Z8go. J. WALTER FEwKEs. 
centrum in a transverse direction, and are continued by a rodlike bone 
Just below this is a second delicate bony thread. 
In the caudal region the processes and their continuation dimfnish, 
while the ventral thread becomes larger and forms the hzemal arch. 
