64 Addison E. Verrill, 



of the plunger and socket, which seem to be special organs used 

 in making the sound. The sound has been erroneously said to be 

 made by the sudden withdrawal of the plunger, like drawing a cork 

 from a bottle. 



This was the view held by Saville Kent and by Wood Mason. 

 Mr. Louis Mowbray, who had charge of the Bermuda Aquarium, 

 wrote to me that this is also in accordance with his observations. 

 But Professor Brooks (Mem. Nat. Acad. Science, v, p. 329) 

 stated that the noise is made by suddenly shutting the claws 

 together, and says that he has repeatedly seen them make it in this 

 way. Mr. G. Brown Goode, in his earlier account, implies the 

 same method. My own attention was not particularly directed to 

 this subject, when in Bermuda, though I often saw many species 

 alive, both in aquaria and in the sea, but it appeared to me that 

 the sound was made by closing the claw very suddenly, as if by a 

 spring, something like the snapping of a gun lock. 



FIGURE 5. a, Alphcus annillatnx Edw.=.-/. lancirostris Rankin ; b, A. 

 candei Guerin; c, Synalpheus goodei Cout. ; d, A. formosus Gibbes. 

 All from Bermuda. Enlarged. By A. H. V. 



M. Coutiere (1899) who had unusual opportunities to study 

 numerous Red Sea Alpheidce, demonstrated that the sound is pro- 

 duced by suddenly closing the claw. He has also shown that the 

 adductor muscles of the dactyl are very strong and so arranged 

 as to produce the effect, while the opposing muscles are slender. 

 He believes that the sucker-like structures on the posterior end 

 of the dactyl and opposite part of the palm, as described above, 

 are for the purpose of holding back the dactyl until the muscles 

 have brought some strain to bear, so that when released the dactyl 



