
1890.] Excavations by Sea-Urchins. 3 
Panama, Australia, Mauritiusand Reunion. Not a single instance 
is recorded from North of Florida on the Atlantic seaboard of 
North America, with the exception of those from Grand Manan 
reported in the present paper. 
Although it is well known that the sea-urchins of several species 
are able to excavate holes in solid rock, that habit has not 
been see well noted in our common sea-urchin S. drobach- 
zensis.* It is indirectly referred to in our text-books on Zodlogy, 
but I have not yet seen a definite statement of a locality on our 
coast where the excavations can be seen and the boring habit 
studied. During the past summer (1889) an interesting speci- 
men of rock excavation was observed by the author on the Island 
of Grand Manan, New Brunswick. A mention of it may not be 
without value to those interested in this subject or who have in 
mind a study of the phenomenon. The Black Ledges, which lie 
near the island of Nantucket, Grand Manan, are rocky reefs bare 
at low tide and wholly covered at high water. These ledges are 
made up of a hard mica schist, through which run veins of 
harder quartzite." These ledges have their surface covered for 
the most part with “sea weeds” belonging to different kinds of 
Fuci and Laminariz, and although not exposed to the full force 
of the sea from the Bay of Fundy, are still at times beaten by a 
heavy surf. The sides of the Black Ledges are thus broken or 
eroded here and there, so that many pools and deep clefts or 
recesses are forced in them. These recesses are in no way char- 
acteristic, but take the form of simple niches in the rock, wholly 
or partially walled in by the bowlders which lie strewn about, 
and are often simply natural depressions or basins in the rock. 
They are generally small, and often have overhanging walls. One 
of these depressions, which can be visited at low tide only, shows 
the work of the sea-urchin in rock excavations in the clearest 
manner. The rock on the sides of which the depressions are 
MAA = of the Echini, p. 706) that Strongylocentrotus purpuri 
ratus 
has this “habit on coast of “ California.” The kind of rock on which the excavation 
takes place and the name of the observer not given. 
15 This quartzite is found in several places on Grand Manan in such quantities as to im- 
part a white color to the cliffs, and to it may possibly be traced local names, as White 
Head, given to'a well known island lying off the coast 

