NO. 1788. -NORTH AMERICAN ERQASILIDJE—WIL80N. 323 



minal joint is the longest and is well armed with setae; there is also 

 a large seta on the ventral surface at the end of the third joint. 

 The second antennae are still biramose, the exopod exactly Hke that 

 of the nauplius, wliile the endopod has become three-jointed, the 

 joints diminishing regularly in size, and the setae wdth which they 

 are armed increasing as regularly. The masticatory process from 

 the basal joint of these appendages has increased in size and is now 

 armed with two large claws of about the same length. 



The right and left antennae in these first two pairs are attached 

 close to the lateral margin of the head, leaving a Avide space between 

 their bases. Tliis space is entirely filled by the large, transversely 

 elhptical upper lip, which carries a row of stiff 

 hairs along its posterior margin (fig. 35). 



In the tliird pair of appendages the exopod 

 and endopod remain practically the same as be- 

 fore, but the masticatory process has completely 

 changed. It is now flattened and triangular, 

 one angle serving as a point of attachment to fi«-35.-labeum of first 



,, , 1 1 -1 c 1 (■ J 1 J 1 1 METANAUPLIUS LARVA. 



the endopod, while from each of the other angles 



proceeds a large plumose seta, with a tliird smaller one at the center 



of the side between them. On these three setae and on two others 



wliich project inward from the inner margin of the basipod the 



plumose hairs are attached in pairs with long intervals between 



them. 



In addition to these three pairs of appendages the metanauplius 

 has acquired three others, two pairs of maxillae and a pair of maxil- 

 Upeds. The fii'st maxillae are just behind and close to the bases of 

 the mandibles, where they easily escape notice. They are not 

 shown in figure 34, being concealed by the bases of the mandibles, 

 but may be seen in figure 36. The rest of figure 34 showed so well 

 it was considered better to secure the drawing rather than risk its 

 entire loss by trying to manipulate the mandibles. The latter are 

 uniramous processes, one-jointed, and tipped with two spines. 



The second maxillae are some distance behind the first pair, are 

 one-jointed, and bilobed at the tip. The outer ramus is longer than 

 the inner, and is armed with two large setae, the outer of which 

 reaches back beyond the tips of the setae on the anal laminae ; the 

 four endopod setae are much shorter. The maxillipeds are very rudi- 

 mentary and consist of a mere knob projecting slightly from the 

 ventral surface and armed with two short setse. But that knob is 

 very distinctly posterior to the notch in the lateral margin of the 

 cephalothorax, which marks the dividing line between the cephalon 

 and the first thoracic segment. 



Here, then, is another species to add to those already described by 

 Hansen, Giesbrecht, and Glaus, in which the maxillipeds are definitely 



