MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 373 



far north as Virginia. From Florida and Cuba nine species are recorded. I have found twelve 

 species of tbis prolific genus, or about one-half the number described for the whole American con- 

 tinent, inhabiting the beautiful little reef of growing coral called Dix Point to the eastward of 

 Nassau Harbor and along the margins of the little bay which was just in front of our laboratory. 

 Another species (A. icebsteri Kingsley), first reported from Florida, was also discovered on Greeii 

 Key reef, a few miles from Nassau. 



From collections which I made at Abaco and Andres Islands, I am led to believe that the 

 different species are quite generally distributed in the Bahamas, and as these islands have prob- 

 ably been largely populated from the South, we may expect the same forms to occur at Cuba and 

 at other West Indian Islands. This genus, however widely distributed, is essentially lropic,.il and 

 abounds in all coral seas. Of the great family of the Crustacea which make their home on the 

 submerged reefs of growing coral, Alphcus is perhaps the most prominent and thoroughly charac- 

 teristic. They pop out of almost every rock which is brought up from the bottom, and every loose 

 head or block of growing coral, with its clusters of alga-, sponge, and sea fans, which you pull 

 from the reef, resounds with the click of their little hammers. 



Some of. these animals lead a semi-parasitic life in sponges, or seclude themselves in the porous 

 limestone which forms the solid floor of the beach, and others, again, live under loose shells and 

 stones in the white coral sand. Some are highly and beautifully colored, and with few exceptions 

 the pigment is characteristic of the species for any locality. In all cases the claws of the first 

 pair of walking legs are enormously enlarged and serve as formidable weapons of defense so re- 

 markable in this genus, and in most there is the greatest disparity in the size of these claws, one, 

 either the right or left, being the larger. One species, the habits of which are peculiar, carries 

 the larger of these claws so folded under the body as to be completely concealed. It can, however, 

 quickly withdraw this weapon and make a rapid thrust, when an enemy comes near.* By the scis- 

 sor-like blades of the large claws a sharp metallic report is produced. This is true of nearly all the 

 species, and so abundant are many in these islands that a constant fusilade is kept up along some 

 of the shores at low tide. This snapping propensity is shared by both sexes whether in or out of 

 the water, and it is undoubtedly correlated with their pugnacious habits. If two males or females 

 of the same or different species are placed in the same aquarium, they will dismember each other 

 in a very short time, and one is usually literally torn to pieces. 



The sounds emitted by Alpltcus hcterochelis are the loudest I have heard from any member of 

 this genus. We frequently kept this species in glass dishes in our room for several days at a time, 

 and sharp reports like the explosion of a small torpedo or pop gnn were heard at intervals through 

 the day and night. It sometimes, swims with its large claw so widely opened as to suggest dislo- 

 cation. This weapon then reminds one of a cocked pistol, and the report apparently follows in 

 the same way that the click follows the impact of the hammer on the lock. I have given this 

 mattter no closer attention, but find that Mr. Wood-Mason, who is quoted in a notice on " Stridulating 

 Crustacea"! in "Nature," (05). has offered another explanation. According to this observer the 

 sound always accompanies a sudden opening of the claws to their fill lest extent, and may be caused 

 either by impact of the dactyle upon the joint to which it is articulated or "by forcible withdrawal 

 of the huge stopper-like tooth of the dactylopodite from its pit in the immovable arm in the claw." 

 It seems most probable to me that the sound. is caused by impact, and most likely by the rapid 

 closure of the finger into its socket. :f 



* This species is entirely new. The large concealed claw suggests a poison .apparatus. The " fingers " .are ex- 

 ceedingly slender and sharp at the points. Although kept for over a, week in an aquarium it emitted no sounds. 



t According to Wood-Mason sound-producing organs in Crustacea were first brought to notice by Ililgrndorf, in 

 V. der Decker's "Roiseu in Ost-Afric.a (Criistaceen)," and were afterwards observed by himself in his dredging ex- 

 pedition to the Andaman Islands. The Btridnlating organs scrapers and rasps may bo either on the carapace and 

 appendages or on the appendages alone. 



t Hoth Kent and Wood-Mason speak of the sounds emitted by the Alphei as if produced by the extension or 

 opening of the claw. As pointed out above, it is just the other way, the sound following upon the impact of dactyle 

 and propodus, when the tooth of the dactyle is not pulled out of its socket but driven into it. None of the conditions 

 of piston movement are present. The walls and floor of the pit are relatively soft, while the tips of the elaw are 

 dense and stony. The "click" can be artificially produced when the claws are clamped with rubber, whether the 

 " stopper " is present or not. 



