INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 467 



such times of general retreat each one gets into the first hole that he 

 can find. Associated with this "fiddler" another related crab, the Se- 

 sarma reticulata, is occasionally found in considerable numbers. This 

 is a stout-looking, reddish brown crab, with a squarish carapax ; its large 

 claws are stout and nearly equal in both sexes, instead of being very 

 unequal, as in the male "fiddlers." It lives in holes like the "fiddlers," 

 but its holes are usually much larger, often an inch or an inch and a half 

 in diameter. It is much less active than the "fiddlers," but can pinch 

 very powerfully with its large claws, which are always promptly used 

 when an opportunity occurs. 



The Carcinus granulatus (p. 312) of large size may often be found con- 

 cealed in the cavities under the banks undermined by the two preceding 

 species, along the ditches and streams in the salt-marshes. On the 

 marshes farther up the estuaries, and along the mouths of rivers and 

 brooks, and extending up even to places where the water is quite fresh, 

 another and much larger species of "fiddler-crab" occurs, often in abun- 

 dance ; this is the Gelasimus minax. It can be easily distinguished by 

 its much larger size and by having a patch of red at the joints of the 

 legs. Its habits have been carefully studied by Mr. T. M. Prudden of 

 New Haven, but his interesting account of them has not yet been pub- 

 lished. He has also investigated its anatomy. According to Mr. Prud- 

 den this species, like G-. pugilator, (see p. 336,) is a vegetarian. He often 

 saw it engaged in scraping up and eating a minute green algoid plant, 

 which covers the surface of the mud. The male uses its small claw ex- 

 clusively in obtaining its food and conveying it to the mouth. The 

 female uses either of her small ones indifferently. In enlarging its bur- 

 rows Mr. Prudden observed that these crabs scraped off the mud from 

 the inside of the burrow by means of the claws of the ambulatory legs, 

 and having formed the mud into a pellet, pushed it up out of the hole 

 by means of the elbow-like joint at the base of the great claw, when 

 this is folded down. He also ascertained that this crab often constructs 

 a regular oven-like arch of mud over the mouth of its burrow. This 

 arch-way is horizontal, and large and long enough to contain the crab, 

 who quietly sits in this curious door-way on the lookout for his enemies 

 of all kinds. 



This species can live out of water and without food for many days. 

 It can also live in perfectly fresh water. One large male was kept in 

 my laboratory in a glass jar containing nothing but a little siliceous sand, 

 moistened with pure fresh water, for over six months. During this 

 whole period he seemed to be constantly in motion, walking round and 

 round the jar and trying to climb out. He was never observed to rest 

 or appear tired, and after months of confinement and starvation was 

 just as pugnacious as ever. 



Although some of the colonies of this species live nearly or quite up 

 to fresh water, others are found farther down on the marshes, where the 

 water is quite brackish, and thus there is a middle ground where this 



