^U. minax^ (^Gelasimus minax^), ^U. pugnax^ (^Gelasimus pugnax^), ^U. pugilator^ (^Gelasimus pugilator^), the fiddler-crabs. These species [pg283] of fiddler-crabs occur on the Atlantic coast. They congregate in immense numbers, and excavate their holes in convenient localities above the reach of the tides—on salt-marshes, far up the estuaries, and along the mouths of rivers, even where the water is quite fresh. The males have one claw very largely developed; the other chela is small. The former is likened to a fiddle, the latter to a bow, and this, together with the waving motion of the large claw, gives them their popular name. This comparatively enormous claw is a distinguishing feature by which they are easily recognized without other description. The female has claws of small and equal size. These crabs burrow holes in the mud or sand half an inch to two inches in diameter and a foot or more in depth. The upper part is nearly perpendicular, becoming horizontal below, with a chamber at the end. One species, /U. minax/, constructs an archway over the mouth of its burrow, in which it sits and surveys the surroundings, but quickly retreats when danger approaches. The crab makes its burrow by scraping up the mud or sand and forming it into pellets, which it carries under the three anterior walking-feet on the under side, using the legs on the side moving forward, and the fourth one on the other side, to climb out of the hole. After peering cautiously about, the crab emerges, and carries its load four or five feet away before dropping it; then again looks about before quickly running back; and, finally, turning its stalked eyes, looks in all directions and suddenly disappears, soon to return with another load. The burrows cover considerable areas, and the crabs are so abundant that the marshes and shores sometimes seem to be alive with them. When alarmed, they lift the large claw and run sideways, after the manner of all crabs, to their holes, and, as many are likely to retreat into the most convenient one, the owner often finds his burrow occupied by other tenants, whom he unceremoniously proceeds to pull out. /U. minax/ ranges from southern New England to Florida, and lives on salt-marshes farther away from the sea than the others, and often where the water is quite fresh. It is larger than the other species, and can be distinguished by a red patch at the joints of the legs. It is a vegetarian in diet, living on small algæ. This is the species which constructs a little observation-house over the mouth of its burrow. It can live out of water, and without food, for several days. /U. pugilator/ lives on sandy and muddy flats and beaches near high-water mark, where the sand is compact and somewhat sheltered, and ranges from Cape Cod to Florida. This species, like /U. minax/, is a vegetarian. /U. pugnax/ is exceedingly abundant on muddy banks and ditches of