DECAPOD CRUSTACEANS OF THE WEST INDIES 97 



scarcely more than 1 foot in depth) along Mannet's Gutter on tlie 

 Clarke Hall Estate, where regular visits were made over a period of 

 several weeks, not once was more than one M. carcinus observed. On 

 tliree occasions, the single M. carcinus in the pool was collected 

 during the day and on the following days the pool was re-examined to 

 determine whether or not another individual had moved into it. In 

 one of the tliree pools, another shrimp moved into it during the night; 

 the other two were repopulated two days later. In yet another pool, 

 two shrimp were taken from beneath the same stone three days 

 apart, and for the next three days, unsuccessful attempts were made 

 to find a thhd one under the rock. There are no data available, to our 

 knowledge, to indicate what factors promote or discourage migi-ations 

 of individuals along the course of a stream or to determine whether 

 or not they migrate in both directions. 



In contrast to the smaller pools, the larger ones, those with surface 

 areas of at least 20 square feet, may harbor more than one individual 

 of M. carcinus. In one such pool (sm-face area of approximately 100 

 square feet) on Mannet's Gutter, the better parts of several days 

 were spent observing the composition of the decapod population. At 

 one time there were four M. carcinus, one large one and tliree that 

 were considerably smaller. Whether or not these four shrimp had 

 divided the pool among themselves is not know, but when an earth- 

 worm was dangled into the water, the three smaller ones came toward 

 it from different directions; a short time thereafter, the fourth shrimp, 

 by far the largest, appeared from under the largest overhanging stone 

 in the pool and from the same direction from w^hich one of the smaller 

 ones had come. There was no question, on any of the occasions during 

 wliich this group was being observed, that the largest sluimp, while 

 tolerating the presence of the other tlu'ee in its pool, was the master 

 of it. The smaller ones swam or backed quickly away when the largest 

 one approached. 



Distribution. — Florida and Texas, U.S.A., to Estado de Santa 

 Catarina, Brazil (Cuba, Jamaica, Hispaniola, Puerto Rico, Saint 

 Thomas, Saint Croix, Saint Martin, Dominica, Saint Lucia 1., Saint 

 Vincent, Barbados, Trinidad, Bonaire, Curagao, Aruba). 



Dominica Stations: 1-4, 7, 8, 11, 12, 14, 22, 23, 30, 43, 50, 54, 66, 

 68, 89, 95, 96, 109 (0-1,900 ft.). 



Remarks. — Of the 31 females collected on Dominica, the majority 

 (20) were taken in January, February, and March. Egg-bearing 

 specimens, however, were found only on October 25, 1964 (2 of 6 

 females) and May 13, 1966 (1 of 3 females). This suggestion of a 

 breeding season is in agreement with the observations of Lewis, 

 Ward, and Mclver (1966) on Barbados, where ovigerous specimens 

 were collected in every month from May through October, but none of 



