ISOPODS OF NORTH AMERICA. 



235 



of antennae are composed of eleven articles, the last three being very 

 minute. The articles of both pairs of antennae are greatly dilated and 

 flattened. The second antennae extend to the posterior margin of the 

 head. The maxillipeds have a palp of two articles. The palp of the 



FIG. 237. CERATOTHOA IMPRESSA. a, MAXILLIPED OF FEMALE. , x 27s-. 6, SECOND MAXILLA, x 27. 

 c, FIRST MAXILLA, x 51|. d, PALP OF MANDIBLE, x 27j. 



mandibles is very large and conspicuous and is composed of three 

 articles. The second or posterior maxillaa are very large and con- 

 spicuous, are bilobed at the tip, both lobes being furnished with small 

 hooks. 



The first four segments of the thorax are large and about equal in 

 length; the fifth segment is half as long as any of the four preceding 

 segments; the sixth and seventh segments are very short in the 

 median dorsal line and each is about one-half as long as the fifth 

 segment. The first thoracic segment has the antero-lateral expansion 



FIG. 238. CERATOTHOA IMPRESSA <, AFTER SCHKEDTE AND MEINERT). a, YOUNG OF THE SECOND 

 STAGE, b, YOUNG OF THE THIRD STAGE, c, YOUNG OF THE FIRST STAGE. (ENLARGED.) 



produced in a carinated process, produced outward and forward and 

 terminating acutety a little anterior to the antero-lateral expansion of 

 the segment. The epimera are distinctly separated on all the follow- 

 ing six segments. In the second segment they are directed forward 



