ISOPOD8 OF NORTH AMERICA. 



839 



also half as long as the fourth; the sixth and sovonth arc slightly 

 shorter than the fifth. There are two long spines on each one of the 

 thoracic segments, one on each side of the median longitudinal 

 line. The lateral parts of the first segments are l)roadly expanded and 

 surround the posterior portion of the head at the sides. The epimera 

 of the second.. third, and fourth segments are small, l)ut distinctly 

 separated from the segments; they occup}' the antcro-lateral angles of 



Fig. 3tj7.— Arcturus baffini (After G. O. Sars). a, Anterior part of body, with first pair of 



ANTENNA AND ORAL APPENDAGES VIEWED FROM BELOW, b, FlK.ST ANTENNA. C, BASE OF SECOND 

 ANTENNA. (/, ADVLT FEMALE, FROM ABOVE, r, FIRST LEG. /, SECOND LEG. J7, POSTERIOR PART OF 

 BODY, VIEWED FROJf BELOW (oNE OF OPERCULAR VALVES REMOVED), ll, TWO SENSORY APPENDICES 

 OF FIRST ANTENNA. (, LaBRUM. J, FLAGELU'M OF SECOND ANTENNA, k. MANDIBLES. /, ONE OF 

 ANTERIOR PLEOPODS. Ill, TERMINAL BRANCHES OF OPERCULAR VALVE (INNER SIDE). )i, SEVENTH 



LEG. o. One of posterior pleopods. p. First maxilla, q. Labium, r, Second maxilla, s, Max- 

 iLLiPED. /, Terminal claw of seventh leg. u, Lateral view. 



the segments and are not visi])le in a dorsal view. The epimera of 

 the last three s(\onionts are large and also distinctly separated; they 

 project at the sides of the segments, being pi'oduced in long, acute 

 processes, and are conspicuous from a dorsal view. 



The first two segments of the ahdomen are short, and each is pro- 

 vided with two dorsal spines, one on either side of the median longi- 



