326 THE AMERICAN NATURALIST. [Vor. XXXIX. 
the investigation may serve to explain the presence in these 
notes of material that might otherwise seem trivial. It is 
believed that nothing has been admitted which does not bear on 
the general question. 
Limpets are found on the entire New England coast and 
northward to the Arctic Ocean. Comparatively rare and local 
south of Cape Cod, they increase in numbers and in size as one 
passes northward until at Eastport, Maine, they are one of the 
most abundant of thelittoral molluscs. They are found between 
tide-marks in pools and also in such shaded places as provide 
them at once with coolness and moisture. The vertical face of 
a rock heavily hung witb dripping Fucus or the under surface of 
the larger beach pebbles are attractive spots. Although they 
are to be found occasionally where the water is at least slightly 
fouled by sewage, as in the estuary at Beverly, they are far more 
abundant in that which is clean and pure. 
So far as reported they seem to reach their maximum size in 
the region of Eastport, which is bathed by the cool waters of the 
Arctic current. On the Massachusetts coast a limpet an inch 
long is a giant but at Eastport they not rarely reach a length of 
32 mm. The first explanation of this fact which presents itself 
is of course that the cooler water presents the optimum temper- 
ature for these animals; this is not, however, the only possible 
explanation. The Arctic current is not only cooler but more 
equable in temperature than more southern waters. At East- 
port the maximum yearly variation in temperature of the water 
is about 12° C. (32.5°-54° F.): at Boston it is nearly 23° C. (29°- 
70 F.! Limpets living entirely below tide-mark would there- 
fore enjoy comparatively equable temperature conditions at East- 
port. This would not, however, be true for those living between 
tide-marks, for the annual variation in temperature of the air at 
Eastport is often as much as 35? C. (47-67? F.) — 10° C., it may 
be,in a single month. Bathed twicea day by the water, exposed 
twice a day to the air, such individuals in spite of the compara- 
tively cool places which they affect, would be exposed to condi- 
' These figures are deduced from the records of the U. S. Weather Bureau at 
Eastport and Boston, for the years 1887-89, the only years during which ob- 
servations of water temperature were made. 
