MONSTEE PEAWNS 247 



the carapace armed with two antennal teeth, one 

 above the other ; the second trunk-legs with the 

 wrist long. 



Palcemonella, Dana, 1852, has one tooth on the frontal 

 margin, and a second on the hepatic region nearly 

 in the same horizontal line ; the second trunk-legs 

 with the wrist not long. 



Bracliyccurpus, Spence Bate, 1888, has one tooth on the 

 frontal margin, and a second on the hepatic re- 

 gion, below the horizontal line ; the second trunk- 

 legs with the wrist short. 



Palcemon carcinus is found in American rivers ; Palcemon 

 lar, the second in the list of Fabricius, in the East Indies. 

 Palcemon jamaicensis has been obtained by Mr. Osbert 

 Salvin from Lake Amatitlan, 'where it reaches a large 

 size and forms an important article of commerce in the 

 market at Guatemala.' Of Palcemon heterochirus, Wieg- 

 mann. Stimpson remarks that 'this is another of the 

 large freshwater shrimps of Mexico. They frequently 

 attain a length of two feet, including that of the chelopoda, 

 which are at least as long as the body.' Other species 

 range over the isles of the Pacific and Australia. In this 

 genus the most striking feature is the elongation of the 

 second legs in the male, which not infrequently even 

 exceed the total length of the animal's body ; a specimen 

 of Palcemon lar may measure about five inches from the 

 front margin of the carapace to the tip of the telson, and 

 carry limbs eight inches long. 



Palcemonella, Dana, has the rostrum slender instead of 

 deep as in the other three genera, and the ' palp ' of the 

 mandible perhaps only two-jointed instead of three-jointed. 

 Dana's two species tenuipes and orientalis are both from 

 Eastern waters. 



To Leander must be transferred the three species which 

 Bell calls Palcemon serratus (Pennant), Palcemon squilla 

 (Linn.), and Palcemon Leachii, Bell, the last of these be- 

 coming Leander Faln-idi (Rathke). Norman now considers 

 that his Palcemon minans from Guernsey, may be merely 

 an abnormal specimen of Leander squilla. Palcemon vanans, 



