I. '21. 



37 



niav always ])c 



distinguished 



by certain 



two species they 

 characters which remain constant. Milne-Edwards and 

 Bouvier, in their admirable account of E. variabilis (1900), 

 give tlie following characters for the separation of the two 

 species : — 



E. excavatus. 



1. Four unpaired pleopods 

 in the male. 



2. The left chela has a pro- 

 minent carina, on the outer 

 side of which there is always a 

 smooth hollow. 



3. Xear the inner border of 

 the right chela the inner face is 

 smooth, granular, or tubercu- 

 lar up to the very edge without 

 interruption. 



4. The process at the outer 

 side of the second joint of the 

 antennal peduncle does not 

 reach the base of the terminal 

 joint. 



5. The lower surface of the 

 merus of the right cheliped is 

 covered with hairs which are 

 much longer than the granules 

 on the surface. 



E, variabilis, 



1. Three unpaired pleopods 

 in the male. 



2. No smooth hollow, and 

 the carina is less prominent. 



3. Xear this edge there is 

 on the inner face, a line of 



granules or denticles which is 

 separated from the edge by 

 an almost smooth space. 



4. The process reaches or 

 passes the base of the terminal 

 joint. 



5. The lower face of the 

 merus is covered with very 

 short hairs. 



The most reliable characters in this table and the easiest to 

 use are those numbered 1 and 4. 



It is with the var. meticulosus, Roux, of E. excavatus that 

 E. variabilis is most likely to be confused. Milne-Edwards 

 and Bouvier (1900) give the following summary of the characters 

 of the typical form and of the variety : — 



" E. excavatus (typical form) — Characterized by two 

 deep excavations, usually quite smooth, which are hollowed 

 out in the propodite of the right cheliped, and are bounded 

 by three carinae, one median and two marginal, w^hich 

 are high and sharp. The dactyl is also excavated above. 

 The carina of the left chela is always smooth and sharp. 



E, excavatus, var. meticulosus — Right propodite less 

 deeply excavate. The concavities of this hand are more 

 or less roughened and granular in part of their length, 

 especially posteriorly. The three carinae are of medium 

 size, thick, obtuse, and granular on the edges, especially 

 in the ease of the middle one. The median carina of the 

 left hand is always rather obtuse and granular ; as to the 

 lower edge of the same hand it is less drawn out and much 

 less sharp than in the typical form of the species." 



