Decapod Crustacea of Bermuda, Part II . 65 



will close more violently. In fact the effect is something like the 

 snapping of the hammer of a gun lock. 



The sucker-like structures, like the large size of the plunger, are 

 characteristic of the species that make the loudest sounds. The 

 sucker-like organs are not found in Synalplieus. though the plunger 

 and socket are present. Most other genera of the family lack 

 these organs and make no such sounds. 



All the seven Bermuda species can be distinguished by the form 

 and sculpture of the large chela. Other useful characters are found 

 in the form and size of the rostrum ; the presence or absence of ocu- 

 lar spines ; the size and form of the antennal spines ; the proportions 

 of the carpal joints of the second pair of legs; the form of the 

 telson, etc. All the species have a fringe of long plumose hairs, 

 and some slender plain ones, on the telson and uropods, usually 

 with small spinules at their bases. See pi. 27, fig. is. Some have 

 conspicuous and characteristic colors in life. 



This genus is very abundant in all tropical and subtropical seas, 

 especially on coral reefs. About 100 species are known. Some of 

 them are widely distributed, apparently occurring both in the 

 Atlantic and Pacific Oceans in some instances. 



They especially abound in the cavities in coral reefs and in holes 

 in dead corals. Others are found under stones, or sometimes 

 burrowing holes in mud or sand. Several species inhabit the 

 exhalent orifices and internal cavities of living sponges ; a few 

 inhabit the gill cavities of mollusks. They are usually remarkably 

 pugnacious. When confined together they often destroy each 

 other by a single stroke of the big claw. 



The species seem to vary greatly in respect to the complexity of 

 their development and the condition in which the young hatch from 

 the eggs. Most have small eggs and complete metamorphoses, 

 hatching as zoe'as, or in the mysis-stage; others come from the 

 large eggs in nearly the adult form. 



According to Brooks and Herrick, who have made detailed 

 studies of several species, the same species (e.g. A. hctcrocli&lis) 

 may vary in this way in different localities,* but some of the forms 



* Memoirs U. S. Nat. Acad. Set., vol. v, pp. 361-463, 1892. Other species 

 studied by them were "A. minus?'=A. packardii: Synalpheus saulcyi var. 

 brevicarpus: and S. longicarpus. Their identifications of some of the 

 species were very unreliable. 



