o4. Bulletin American Museum of Natural History [Vol. LIII 
spines, often in threes and fours from a common base; C. cooki has but a 
few low scales on the upper margin carrying anteriorly tufts of long hairs. 
The propodus of the outer left leg of C. africanus is more or less 
cylindrical, the rounded outer and upper faces passing over rather evenly, 
one into the other; in C. cooki the outer face is more flattened, and there- 
fore forms a blunt angle with the upper face, marked by a narrow smooth 
band lying between the upper row of hair tufts of the outer face and the 
external, or outer row of the upper face of the propodus. 
Moreover, the ambulatory dactyls of C. cookz are less slender, less 
curved, and shorter. In the two specimens compared, though the an- 
terior portions of their carapaces are approximately the same in length, 
the dactyls of C. africanus are from one-third to one-half longer than in 
C’. cookt. 
‘On certain parts of the sandy shore along the bay just east of 
Banana Peninsula one can see during low tide many apparently empty 
shells, scattered about, of two varieties of Potamides fuscatus and a few 
of Thais coronata. They are inhabited by hermit crabs of chiefly two 
species, Clibanarius cooki and C. africanus. On cloudy or rainy days they 
generally remain wherever, or not far from where, the tides strand them. 
But, if bothered by the heat of the sun, these shells move into shady 
patches near mangroves or grass-covered places. In such favored sites 
they form, for the time being, small heaps of a hundred and more, as 
if some one had deliberately brought them together (PI. IX, fig. 1). Before 
the tide reaches them again, however, they disperse. 
“Tt is interesting that on Bulabemba Island, just across Banana 
Bay, one of the very shells these hermit crabs use, Potamides fuscatus, 
at times comes together in numbers, often exceeding several thousand. 
This happens only during the dry season (July-September) when certain 
parts of its habitat as well as the lagoons are drying out. They crawl, 
however, into available depressions where they remain. To prevent the 
sun from heating up their shells they keep turning about, the dry, whitish 
shells on top seeking to work themselves under the moist, dark ones 
below. But, even so, late in the afternoon considerable moisture has 
“ been removed by the sun. The Potamides certainly could not withstand 
the daily repetition of such a baking process were it not that through the 
hygroscopic action of the salt thus crystallized a large amount of moisture 
is retained every night-from the heavy dewfall.” (H. L.). 
