DEC APOD A. 

 MACROURA. 



PALSEMONIDtf. 



GENUS PAL/EMON. FABB. 



ASTACUS. Pennant. 



PAL-EMON. Fabr., Latr., Lam., Leach, Edw. 



Generic character. External antennce placed beneath, and a 

 little to the outer side of the internal ; the lamelliform palp very 

 large, nearly oval, rounded and ciliate at the apex and armed with 

 a spine near the extremity of the outer margin. Internal an- 

 tennae inserted above the external ; the first joint of the peduncle 

 very large, depressed, excavated on its upper side to receive the 

 eyes, and armed on the outer side with a strong spine; the two 

 following joints large and cylindrical, the last bearing three setse 

 of which two are very long, and the other very short and curved. 

 External pedipalps of moderate length, pediform, slender, terminat- 

 ing in a slightly curved nail. First pair of feet very small and 

 slender ; hand didactyle : second pair also didactyle, much larger 

 than the former; the remaining pairs simple, monodactyle. Cara- 

 pace of moderate size, broad, terminating in a long, laterally flat- 

 tened rostrum, which extends usually beyond the peduncles of 

 the antennae. Eyes large and projecting. Abdomen large, dimi- 

 nishing regularly towards the tail, and rounded on the upper 

 surface : the terminal segment, which forms the middle portion 

 of the tail, triangular. Abdominal false feet very large ; 

 those of the first pair furnished with a large ciliated scale, and 

 a much smaller one; the others with two scales, which are also 

 distinctly ciliated. 



ALTHOUGH most of the species of this genus are of 

 moderate size, there are some inhabiting the tropical re- 

 gions which may almost rival the larger Astacidtc. The 



