
4 The American Naturalist. [January, 
formed is inclined at a small angle to a perpendicular, and is 
almost bare of algz, so that the boring can be seen without 
difficulty. The basins ordinarily have water in them at low tide. 
There is no coralline on the floor of the cavity. 
The number" of sea-urchins at Grand Manan is very great, as 
was long ago noted by Dr. William Stimpson. In many places it 
is impossible to see the bottom of the bay, so densely populated 
is it with these animals. In the rock recess above referred to, the 
surface of the shelf before the animals were disturbed was 
paved with sea-urchins, and the number of examples of excava- 
tions which they had formed were therefore very numerous. The 
cavities made by the sea-urchins impart to the rock an appearance 
not unlike the upper surface of honeycomb, with this difference, 
that the bounding rim of each excavation is always ring-shaped 
and entire. 
The separate excavations which are shown in the figure, some- 
times with the Strongylocentrotus in situ, sometimes with the same 
removed, are never very deep, but are undoubtedly made by the 
echinoderm. Their surfaces are concave, corresponding with the 
convexity of the sea-urchin’s body, and very smooth, as if freshly 
cut or worn. They are often larger than the sea-urchin inhabit- 
ing them, and roomy enough to admit a free motion of the 
contained animal. In no instance is the depth of the depression 
greater than the smaller diameter of the animal. The edge ot 
16 The wealth of asteroid and ophiuroid life at Grand Manan is also marvelous to one 
who has confined his attentio a to collectin ecting in Menachusettė aK ae bona of the 

The 
dredge near High Duck Island was gorged with specimens of Ophiopholis PET 
with here and there specimens of Ophiacant Soe and ppap ipes ES squamata, 
although common, is not found in such multitudes. to believe from its 
extreme rarity that the Comatula recorded b Stimpson paw Gast) d Manan is astraggler. 
Certainly the genus is very rare in these waters. Leptasterias, Solaster, Crossaster, and 
7 7 ster also oc is 
Manan genus of starfishes, and a colony | of its young, fifty or more in number, were 
found by M. J. S. Owens on the under side of the rock at low tide near Nantucket. 
This n in he colonial en pE the young of this genus is an interesting 
ted with i ier stages. Ctenodisci 

ehispaias wie tok t seen by us at Grand Manan, although others have found it there. It 
was, however, taken at Eastport in tdredging. On the geen the dredging at 
Grand M i ich fi i ya f starfish =e ophion life as ' The 
z = 


