230 A HISTORY OF RECENT CRUSTACEA 



vnrieiies of one great type.' In Ghiphocrangon aculeaiua, 

 A. Milue-Edwarrls, the carapace is ornamented with eight 

 cavinse, but in GLyphoorangon granulosus, Spence Bate, 

 there are five on each side of the median line, besides a 

 small central one on the rostrum. The telson in this 

 genus is described as a long bayonet-shaped organ, which 

 the animal during life has the power of locking in a fixed 

 position, so as to render it a very powerful weapon of 

 offence, and of again unlocking at its own will. When 

 fixed for striking it is supported in position by having a 

 strong cusp or tubercle on its dorsal surface brought into 

 contact with a curved process of the preceding segment. 

 Glyphocmngon rimapes, Spence Bate, was trawled in the 

 South Atlantic from a depth of 1,715 fathoms, and it is 

 noted as an instructive coincidence that in Willemoesia 

 leptodadyla, obtained in the same haul, the organs of 

 vision are reduced to a rudimentary condition, while in 

 Glyphocmngon they are unusually large. 



Nilwides, Paulson, 1875, is distinguished from Nika by 

 having an exopod on the first pair of feet, and by subdi- 

 vision of the fourth joint as well as of the fifth in the 

 second pair. The type Nilcoides Dance is from the Red Sea. 



Family 2. — Alpheidce. 



The rostrum is minute or of moderate size ; the eye- 

 stalks are short, and more or less covered by the projection 

 of the frontal margin of the carapace ; the mandibles have 

 a cutting edge distinct from the molar process, and a one- 

 or two-jointed ' palp ; ' the first pair of trunk-legs are 

 robustly chelate, sometimes unsymmetrical, the second pair 

 are long and slender, minutely chelate. 



Spence Bate makes a two-jointed mandibular ' palp ' 

 a character of the family, but in describing his own genus 

 Paralpheus, he says that it is uniarticulate, and in Alphms, 

 Fabricius, 'three-jointed,' the latter being probably a slip 

 of the pen for two-joiuted. Ten or more genera have 

 been assigned to the family, two of which occur on the 

 coasts of Great Britain. 



Alpheus, Fabricius, 1778, has a short pointed rostrum, 



