ISOPODS OF NORTH AMERICA. 219 



what shorter than first three. First five abdominal segments equal in 

 length. Terminal segment rounded posteriorly. Uropoda longer 

 than terminal segment; branches unequal. Outer branch the longer; 

 inner branch obliquely truncate. Legs similar in structure, with 

 curved dactyli. Color, light brown, densely covered with black spots. 

 Single specimen from Barren Island, Chesapeake Bay. 



Depth. 3 to 25 fathoms. 



Type. Cat No. 23904, U.S.N.M. 



34. Genus NEROCILA Leach. 



Body relaxed, very often flattened. Head posteriorly produced 

 in three lobes, not at all immer >ed. First pair of antenme almost con- 

 tiguous at the base. 



First segment of thorax with the anterior margin deeply trisinuate. 

 Posterior angles of the segments from the second to the last increasing 

 gradually in length, the first of these often but little produced, the 

 posterior ones almost always produced and often abruptly longer than 

 the first ones. The anterior epimera almost always extend to or 

 beyond the posterior angle of the segment; the posterior epimera are 

 produced and acute, but do not reach the posterior angle of the segment. 



Abdomen free, rarely covered at the base or the sides. Legs rather 

 long. 



ANALYTICAL KEY TO THE SPECIES OF THK GENUS NEROCILA. 



a. Terminal abdominal segment quadrate, with post-lateral angles rounded and 



posterior margin acuminate and produced in an acute point. 



b. Body a little more than one and a half times longer than wide. Head as long 

 as wide. Post-lateral angles of all the segments of the thorax are produced 

 backward in long acute processes, increasing in length from the first to the 

 seventh segment. The epimera of the second segment extend beyond the post- 

 lateral angles of the segment; those of the third segment extend to the post- 

 lateral angles of the segment; all the others reach the posterior margins of 



the segments Nerocila acuminata Schioedte and Meinert 



b f . Body nearly two and a half times longer than wide. Head wider than long. 

 The post-lateral angles of only the last two segments of the thorax are pro- 

 duced. The epimera do not extend beyond the posterior margins of the 

 segments, except in the last segment where they almost reach the extremity 



of the post-lateral angles Nerocila calif ornica Schioedte and Meinert 



a'. Terminal segment of abdomen not quadrate; posterior margin not acuminate. 

 6. Last segment of abdomen regularly rounded. Uropoda longer than abdomen. 

 Eyes black, distinct. Head as wide as long, truncate in front. Terminal 

 abdominal segment without median longitudinal carina. 



Nerocila munda Harger 



b'. Last segment of abdomen lanceolate. Uropoda shorter than abdomen. Eyes 

 entirely wanting. Head wider than long and truncately rounded anteriorly. 

 Terminal abdominal segment with median longitudinal carina. 



Nerocila lanceolata (Say) 



See Schicedte and Meinert for the characters of the genus, Nat. Tidsskr. (3), 

 XIII, 1881-83, pp. 4-5. 



