246 A HISTORY OF RECENT CRUSTACEA 



convenience of classification, it seems hardly worth while 

 for the present to separate the Tropiocaridee from the 

 Acanthephyridse. Notostomus and Gonatonotus, two genera 

 established by A. Milne-Edwards in 1881, from the West 

 Indies, are both said to be near Oplopliorus, and both to 

 have exopodal appendages to the feet. Not ostomus perlatus, 

 Spence Bate (see Plate XIII.), is from the Philippines. 



Family 6. Palcemonidce. 



The carapace is dorsally rounded and laterally com- 

 pressed, the rostrum long, laterally compressed, and gene- 

 rally armed with teeth. The eyes are well developed and 

 pyriform. The first antennae have the basal joint dorsally 

 hollowed, with a strong spine on the outer side, and 

 frequently one of the flagella branched ; the second pair 

 have a long and narrow foliaceous scale, its rigid outer 

 margin ending in a small tooth. The mandibles have 

 molar tubercle and cutting edge, and either have or have 

 not a ' palp.' The third masillipeds are pediform. 



The family includes about half a dozen genera, two of 

 which are found in British waters. 



Palcemon, Fabricius, 1798, has been subdivided since 

 its institution, and Stinipson in 1860 rightly recognised 

 that Palcemon carcinvs, the first in the list of species 

 assigned 'to the genus by Fabricius, should be the type. 

 Hence the genus Blthijnis of Philippi, to which this and 

 other fresh water species have been referred, is a mere 

 synonym of Palcemon. The marine species, which have 

 been commonly retained under the name Palcemon are 

 referred by Stimpson to Desmarest's genus Leander with a 

 fresh definition. 



Spence Bate gives a synopsis of the genera into which 

 the original Palcemon of Fabricius has been divided, which, 

 with the necessary modifications, may be thus set out : 



Palcemon, Fabricius, 1798, has one tooth on the frontal 



margin of the carapace, and a second on the 



hepatic region nearly in the same horizontal line ; 



the second trunk-legs with the wrist long. 



Leander, Desmarest, 1849, has the frontal margin of 



