ISOPODS OF NORTH AMERICA. 611 



margin produced in three lobes, the median lobe being small and tri- 

 angular with apex acute, the lateral lobes being large and widely 

 rounded. The eyes are small and composite and situated at the base 

 of the antero-lateral lobes. The first pair of antennae are small and 

 inconspicuous. The second pair have the first article short; the sec- 

 ond is twice as long as the first; the third is equal in length to the sec- 

 ond; the fourth is twice as long as the third; the fifth is one and a 

 half times longer than the fourth. The flagellum is composed of two 

 subequal articles. The second antennae extend to the posterior margin 

 of the fourth thoracic segment. 



The segments of the thorax are about equal in length. The epimera 

 are not distinct from the segments. The lateral margins are straight. 

 The antero-lateral angles of the first segment are produced forward to 

 surround the head, and they extend to the base of the antero-lateral 

 lobes of the head; the post-lateral angles of the first segment are pro- 

 duced backward in acute processes. 



All six segments of the abdomen are distinct. The first two have 

 the lateral parts covered by the seventh thoracic segment. The third, 

 fourth, and fifth segments have the lateral parts produced to continue 

 the oval outline of the body. The sixth or terminal segment is tri- 

 angular with the apex produced in a long acutely terminating process. 

 This segment is 2 mm. wide at the base and 2 mm. long to the end of 

 the apical process. The basal article or peduncle of the uropoda 

 extends just a little beyond the middle of the apical process of the 

 terminal abdominal segment. The inner branch is 1 mm. long, and 

 extends to the tip of the terminal abdominal segment. The outer 

 branch is 1 mm. in length and extends a little more than half its length 

 beyond the extremity of the abdomen. 



All the legs are ambulatory in character. 



In color it is a light brown with a longitudinal row of yellow spots 

 on either side at the place of union of the epimera with the segments. 

 Between the median line and the longitudinal rows are markings of 

 yellow wavy lines. 



1O9. Genus PORCELLIO Latreille. 



Body oval, more or less depressed, very little contractile. Lateral 

 parts of the thorax expanded. 



Head with the antero-lateral lobes well developed; median frontal 

 lobe more or less prominent. Front of head marginate. Eyes gen- 

 erally well developed, dorsally placed. Second pair of antenna long; 

 flagellum composed of two articles, the first usually longer than the 

 second, often equally long. or even a little shorter. 



See Budde-Lund for characters of genus, Crust. Isop. Terrestria, 1885, pp. 82-83, 

 and Sars, Crust, of Norway, II, 1899, p. 176. 



