ISOPODS OF NORTH AMERICA. 



283 



Fig. 295.— Sph.kkoma 

 destructor. man- 

 dibular append- 

 AGE. X 10. 



epimeral parts aro not distinct from tlio soo-nients, arc quite })road, and 

 terminate latei'all}^ in acute angles, which point downward. The 

 seventh thoracic segment bears four tubercles situated in a ti-ansverse 

 line. 



The abdomen is composed of two distinct segments, on the first of 

 which are two tubercles, one on either side of the median line. Suture 

 lines at the sides of this segment indicate three coa- 

 lesced segments. The terminal segment is triangu- 

 larly shaped and rounded posteriorly with an upcurved 

 margin, which extends all around the terminal half 

 of the segment. The whole surface of the a])domcn 

 is thickly tuberculated with low but distinct tuber- 

 cles, each one surmounted with a small tuft of stiff hairs or ])ristles. 

 On the anterior part four large tubercles are situated in a transv^erse 

 line, the two center ones being somewhat closer to each other than 

 to the lateral ones. The ui'opoda extend be- 

 3^ond the extremity of the abdomen, the outer 

 branch being the longer. Both are pointed 

 and similar in shape. The outer edge of the 

 exopodite is provided with four teeth, while 

 that of the endopodite is smooth. 



The legs of this species are in three series, 

 according to structure, the tirst three pairs 

 being alike, the fourth and fifth similar. i:nd 

 the sixth and seventh similar. The legs of the 

 tirst series are long and slender (tig. 294 a)^ 

 with the second joint or basis nearlv cylindrical 

 in shape. The ischium is nearly as long as the 

 basis, and this joint, as well as the merus, is 

 furnished with long straight hairs. The carpus 

 and propodus are likewise long and slender. 

 In the tirst pair the carpus is minute. The 

 legs of the second series, the fourth and fifth 

 pairs, are stout and short, ])eing similar in 

 general form, though differing somewhat in rel- 

 ative proportions. The basis is about half the 

 lenp-th of the entire leg, while the joints following the ischium are 

 very short. In the third series the legs are nearly as long as those 

 of the first series, but differ in size and shape. They are stouter and 

 not cylindrical. 



The whole surface of the body is punctate, and has minute trans- 

 verse rugae between the points of depression. In color it is a dark 

 brown, shaded on the edges with a lighter brown. 

 Ti/pe.— Cat No. 19857, U.S.N.M. 



Fig. 296.— Sph.eroma destruc- 

 tor. X 10. a, Leg of sec- 

 ond PAIR, b, Leg of fourth 

 PAIR, r, Leg of fifth pair. 

 fl, Leg of sixth pair. 



