i6o Natural Historv Bulletin. 



inch lonii. In each case it is strongl}' serrated on its upper 

 edge. The antenna? are enormously lengthened, projecting 

 fully nine inches beyond the end of the rostrum and nearly a 

 foot beyond the eyes. The walking legs are also greatly 

 elongated, and are furnished with tvifts of hair which are said 

 to aid the animal in resting on the soft bottom. This species 

 may be identical with JVcniatocarciniis ensifcriis, but our 

 specimens came from much shallower water than those secured 

 by the "Blake," which were found in from eight hundred to 

 fourteen hundred fathoms. Ours were taken from one hun- 

 dred to one hundred and twenty fathoms. 



Quite a number of specimens of the genus AlpJicns w^ere 

 secured, belonging apparently to more than one species. 

 Most of them were dredged from a depth of over one 

 hundred fathoms, although all the specimens secured by the 

 '•Challenger"" came from depths of less than sixty fathoms. 

 On a previous page I was imable to explain the clicking noise 

 made by the large chelae of these animals. Since that passage 

 was in print, however, I find that Professor W. K. Brooks 

 offers the following explanation: '"The claw or dactyl is pro- 

 vided with a plug which fits into a well or socket in the other 

 joint, and probably serves to prevent dislocation. When the 

 forceps are opened the dactyl is raised so that the plug just 

 rests in the mouth of the socket. As soon as the claw^ is re- 

 leased it is suddenly and violently closed, as if by a spring, and 

 the solid, bony points striking together produce a sharp metal- 

 lic report something like the click of a water-hammer, and so 

 much like the noise of breaking glass that I have often, w hen 

 awakened at night by the click of a little Alphcus less than an 

 inch long, hastened down to the laboratory in the fear that a 

 large aquarium had been broken."^ In speaking of their pug- 

 nacious habits, the same writer says: '-Watching its oppor- 

 tunity, it springs suddenly upon its enemy, instanth' closing its 

 claw with a violent snap and a loud report, and cutting a ver- 

 tical sweep with its sharp edge. I have often seen AlpJicns 



iThe Embrjoloj;}' and Met;unorpht)sis of the Majroura, W. K. Brooks- 

 and F. II. Herrick, \\xi,g 329. 



