NO. 1783. NORTH AMERICAN LERN2E0P0DIDJE— WILSON. 209 



APPENDAGES. 



The firet antennse are attached on the dorsal surface, are cyhndrical, 

 imiramose, and four-jointed. The first and third joints are each 

 armed with a single seta, the second with two, while the terminal joint 

 ends in a cluster of five. 



The second antennae are attached on the ventral surface, beneath 

 the bases of the first pair (fig. 22). They are biramose, the exopod 

 one-jointed with a blunt and smoothly rounded tip armed with a 

 single spine, the endopod two- jointed and ending in a strong curved 

 claw. Between the bases of the second antennae on the ventral 

 surface is the conical mouth- tube. This ordinarily projects down- 

 ward and forward, and reaches a little beyond the anterior margin of 

 the cephalothorax. It is as wide at the base as it is long, and is 

 bluntly rounded at the tip, with a fringe of short hairs around the 

 terminal opening. It is made up of a rather flat and narrow upper 

 lip, and a fluted and grooved lower lip, w^hose edges overlap those of 

 the upper lip, and whose tip is arched into a cyHnder to form the 

 suction opening. This lower lip is made up of two halves which 

 arise from separate protuberances, the paragnaths, on either side of 

 the midline and behind the edges of the upper lip (fig. 16), and are 

 not yet fully fused at the tip. Outside the base of the mouth-tube 

 lie the mandibles and first maxillae. The former are uniramose and 

 one-jointed and are tipped with two short and stout spines. The 

 latter are also uniramose but two-jointed, the terminal joint ending 

 in a single spine. They also carry on their inner margin a short 

 cylindrical palp tipped with two small setae. 



The second maxillae are some distance behind the first pair and close 

 to the margin of the carapace. Each is stout and two-jointed, the 

 terminal joint ending in a long and slender claw bent into a half 

 circle. The maxillipeds are close behind the second maxillae, but are 

 considerably nearer the midline. Each is three-jointed, the terminal 

 joint tii)ped with a stout claw, nearly straight except at the very 

 end. These maxillipeds are the chief organs of prehension and are 

 considerably longer than the second maxillse. 



The two pairs of swimming legs are biramose, the basal joints broad 

 and laminate and furnished with powerful muscles, the rami small, 

 one-jointed, and about as wide as long. The exopods of each pair 

 terminate in four stout and long plumose setae, while the endopods 

 have six. 



INTERNAL ANATOMY. 



Internally there has been but little change from the preceding 

 stage. The frontal filament is now completely developed, and may 

 be seen close to the dorsal surface, with the mushroom end flattened 



ProcN. M. vol. 39— 10 16 



