ISOPODS OF NORTH AMERICA. 



391 



tubercles is a transverse row of three tubercles, the central one being 

 in the median long-itudinal line and larger than either one of the others. 

 The eyes are large and round, composite in structure, and situated 

 a))out the middle of the head, a little distance from the lateral margins. 

 The basal article of the tirst pair of antenna? is somewhat enlarged and 

 almost twice as wide as the second article, which it equals in length; 

 the third and fourth articles are subequal and each is about twice as 

 long as the second article. The first antenna? extend 

 to the end of the fourth peduncular article of the sec- 

 ond antennse. The basal article of the second pair of 

 antennge is inconspicuous from a dorsal view; the sec- 

 ond, third, and fourth articles are successively a little 

 longer than the preceding article; the fifth is about 

 twice as long as the fourth. The flagellum consists of 

 thirteen articles. When retracted, the second antenna? 

 extend to the posterior margin of the third thoracic 

 segment. The maxilliped has a palp of three articles. 



The four anterior segments of the thorax are longer 

 than the last three. Ail the epimera are firmly united 

 with the segments. In the median longitudinal line 

 is a row of large tubercles, one for each segment, 

 triangular in shape with acutely pointed extremities. On either 

 side of the median row of tubercles is a group of six or more tuber- 

 cles, of which the innermost one is larger and more conspicuous than 

 any of the others in the group, so that a longitudinal series is formed 

 of these larger tubercles, one on each segment, and placed one row on 

 either side of the median row of tubercles. The sides of the segments 

 are expanded with lateral margins rounded. 



The abdomen consists of one segment with lateral sutures at the 

 base indicating another joartly coalesced segment. At the base of the 

 segment in longitudinal series in line with the median row of tuber- 

 cles on the thorax are two tubercles. There are about six small 

 tu])ercles irregularly arranged on either side of the median line on the 

 anterior portion of the abdomen. The terminal .segment of the body 

 is pointed at the extremity, the posterior half narrowing rapidly to 

 an acute tip. 



The leafs are more or less similar in structure. 



Flc. 434.— Syxido- 

 tea muricata. 

 Maxilliped. x 

 20i. 



SYNIDOTEA PICTA Benedict. 



Synidotea picta Benedict, Proc. Acad. Nat. Sci. Phila., 1897, pp. 401-402. — Rich- 

 ardson, Proc. U. S. Nat. Mus., XXI, 1899, p. 849; Ann. IMag. Nat. Hist. 

 (7), IV, 1899, p. 269; American Naturalist, XXXIV, 1900, p. 228. 



Localities. — Alaska and Boring Straits. 

 Depth. — 5 to 20 fathoms in sand and rocks. 



