2CG Messrs. J. "Wood-Mason and A. Alcock on 



llie exception of tlie tliiid pair, in wliicli the sixth and seventh 

 joints are in addition fused, and tliere are hence oidy five 

 distinct joints ; those of the fourth pair are formed as in the 

 Crangonidse, but, instead of terminating in a subcheha, end in 

 two equal and movable blades forming a scissors-like organ ; 

 those of the fifth pair, which are the shortest and weakest of 

 the limbs, bear a probably expansile pencil of setas at the 

 distal end of the propodite, which is the functional last joint 

 of the limb, the dactjlopodite being reduced to a minute 

 rudiment ; the sixth, seventh, and eighth pairs form a back- 

 wardly increasing series of walking legs; the five last pairs 

 aie devoid of all traces of cpipodites and exopodites. 



The thorax is firmly articulated to the abdomen by a strong 

 hinge. 



hi addition to ihe functional gills, which are five pleuro- 

 branchige attaclied to the posterior thoracic somites from the 

 tenlh to the fourteenth inclusively, there is present, on tiie 

 arthrodial membranes of the thoracic appendages from the 

 ninth to the thiiteenth inclusively, a series of five small 

 coniccd papilla^, which correspond both in number and in 

 ])Osition to the arthrobranchiai of tiic Glypliocrangonidce, and 

 are, there is little doubt, to be interpreted as vestiges of gills 

 of the same category. 



'J he body is exceedingly spiny and terminates in front in 

 a powerful recurved rostrum, which is toothed on all its four 

 margins. 



PSALIDOPUS, gen. nov. 



Body moderately com|>ressed, in shape somewhat like 

 ruJavion. Integument firmly chitinized though thin, covered 

 throughout dor^^ally, from the apex of tlie rostrum to the end 

 of the pixth abdominal somite, with long symmetrically 

 arranged needle-shaped spines, and between the spines with 

 microscoj)ically small sefaj, -vvhich are evenly and regularly 

 distributed, and give to tlie surface a minutely granulated 

 a])pearance up to the base of the caudal swimmeret, upon 

 Avhich they become developed into a furry pubescence. 



I'he carapace is produced in front into a long ascendant 

 curved rostrum iully twice its own length measured from the 

 Jrontal to the posterior margin in a straight line ; its anterior 

 margin is armed on both sides with four spines, which may 

 be termed the antennnlary, antcnnal, branchiostegal, and sub- 

 branchiostegal spines respectively, and with a stout blunt 

 subtriangular defiexed process, against the iviner margin of 

 which the rudimentary eye-peduncles are firmly retracted; 



