134 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
hulks furnish some crevices and foothold for certain species. 
Gravel and stones cover small areas off the “points” where the gla¬ 
cial hills make out. The rest of the bottom is mud, thickly strewn 
with oyster, qualiog, and “jingle” shells. The “Upper Harbor” 
— almost cut off by a sand-spit — in which the specific gravity of 
the water is at times lowered to 1.006, forms a mud bed, rank 
and black, covered with Ulvae, in which the brackish-water forms 
abound and the transition from marine to fresh-water and to land 
forms is almost imperceptible. 
Professor Yen-ill (’73) has analyzed the fauna of the New Eng¬ 
land region according to environment, and gives a list of Mollusca 
characteristic of each station. Below is given his analysis (slightly 
rearranged) showing the per cent occurrence for each station at 
Coldspring Harbor of his characteristic forms for each station. 
1. Harbors, estuaries , ponds, or marshes .— 
a. Sandy shores and bottoms — 100% 
Muddy shores and bottoms = 88% 
Oyster beds in brackish water — 91% ^=r89%. 
Eel grass in brackish water = 80% 
Submerged woodwork, etc.; brackish water = 87 % J 
b. 
c. 
d. 
-\ 
> 
3. 
d. 
e. 
f. 
<y 
»* 
a. 
b. 
c. 
d. 
e. 
80% 
y 68 % 
74%. 
e. 
2. Bays and sounds .— 
a. Rocky shores = 74% 
b. Sandy shores = 93% 
c. Muddy shores = 78% 
Submerged woodwork, etc. = 74% 
Rocky bottoms = 72 % 
Gravelly and shelly bottoms = 54% 
Sandy bottoms =76% 
h. Muddy bottoms = 71% 
Ocean shores and outer waters .— 
Rocky shores = 54% 
Sandy shores = 90 % 
Rocky bottom = 55% 
Sandy and gravelly bottom = 59% 
Muddy bottom = 38% 
Examination shows that from the “ Harbors, estuaries, ponds, 
and marshes” 89% are present at Coldspring Harbor, from the 
“Bays and sounds” 74%, and from the “Ocean shores and outer 
waters” only 59%. Again, from the shore and shoal-bottom 
J 
^ = 59 %. 
