NO. 1783. NORTH AMERICAN LERN.^OPODID.l^— WILSON. 213 



Tlie general shape of the female is that of a spindle, the thickest 

 portion being through the bases of the maxillfe and maxillipeds, the 

 anterior cone much shorter than the posterior. 



The first thoracic segment has separated from the head as dis- 

 tinctly as any of the others and is as wide as the cephalon; the others 

 diminisli in regular order backward. 



The five segments in the body of this larva are thus due to a 

 further separation of the first segment from the head and not to the 

 formation of a new segment. There are really just as many as there 

 were in the first copepodid stage. 



On the dorsal surface the dividing groove between the second and 

 third segments is deeper than the others; on the sides and ventral 

 surface they are all equal. 



The anal lamime are much reduced in size and consist of short and 

 stout papillae, projecting from each posterior corner of the abdomen 

 and tipped with four tiny spines. 



APPENDAGES. 



The first antennae are three-jointed, the two terminal joints having 

 fused, and are only sparingly armed with short setae. 



The second pair (fig. 27) are very similar to those of the free- 

 swimming larva, but project farther. They are made up of a long 

 and stout basal joint and two rami; the exopod is indistinctly two- 

 jointed and ends in a stout curved claw, with an accessory spine at 

 its base; the endopod is one-jointed and tipped with two minute 

 spines (fig. 30). 



The mouth-tube (fig. 26) is more fully developed, the upper lip 

 having increased in size and the halves of the lower lip being thor- 

 oughly fused. The mandibles have entirely changed and are now 

 piercing organs, inclosed within the mouth-tube, but easily slipped 

 outside through the slit in the side of the tube between the edges of 

 the two lips (fig. 31). They are attached at the base of this slit; 

 each is enlarged at the proximal end, tapers into a narrow shank, 

 which is curved over ventrally, and ends in another enlargement, 

 with six or eight curved teeth along its ventral edge. They reach 

 about two-thirds of the distance from the point of insertion to the 

 tip of the mouth-tube. 



The first maxillee (fig. 31) are now attached directly to the sides 

 of the lower lip at a point a little above (distal to) the insertion of 

 the mandibles. Each is uniramose, as long as the mandible, and 

 tipped with two spines of equal length, with a very much shorter 

 one at their base. 



The second maxillae have entirely changed; they still remain 

 short but have lost all trace of segmentation and are much swollen 

 laterally, so that they are three-fifths as wide as long (fig. 20). The 



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