NATfliAL HISTORY OF THE ISOPODA— RICHARDSON. 



G73 



Fir,.23.— .?<:ga quadratas- 



INTS, NEW SPECIES. X 2|. 



equal to the length of one eye. The first pair of antenniv (lig. 24) have 

 the peduncle composed of two short joints of equal length, and a lontr, 

 slender joint ('((ual to the length of the first two taken together; none of 

 these joints arc dilated; the fiagcUuni is composed of twenty-four joints 

 and extends to the posterior margin of the second thoracic segment. 

 The second pair of antenna' have a five- jointed 

 peduncle, the distal end of the fifth joint of which 

 extends to the middle of the first thoracic segment; 

 the fiagellum is composed of twenty-four joints, 

 and reaches the posterior margin of the tliii-d 

 thoracic segment. 



The frontal lamina, or interantennal ])late is 

 cone-shaped, round and flat at its distal end, and 

 produced at its proximal end to an acute point. 

 The segments of the thorax are e(iual in length. 

 The epimera of the second, third, and fourth seg- 

 ments are not pro- 

 duced posteriorly 

 beyond the margin 

 of the segment; 



those of the fifth, sixth, and seventh 

 segments are produced backward. 



There is an arcuate carina on all the 

 epimera which extends from the post- 

 lateral external angle to the internal antero-lateral angle of the oppo- 

 site side. 



All six segments of the abdomen are distinct, the first segment 

 being a little shorter than the four following. The sixth or terminal 

 segment is well rounded posteriorly, with a pronounciKl and wide 

 emargination, quadrangular in shape, in the median line. On either 

 side of this emargination the posterior mar- 

 gin is crenulate for some distance, and is 

 provided with minute spines, about eight on 

 either side. 



The uropoda (fig. 25) are about equal in 

 length, and are not longer than the terminal 

 abdominal segment. The outer ])ran(h is 

 oval in shape, denticulate, and provided with 

 spines on the external and posterior mai-gin. 



The inner branch is unlike the outer branch in shape, and tapers to a 

 narrow extremity at the i)ost-lateral side of the external margin, the 

 external margin l)eing almost straight; this branch is also crenulate 

 and provided with small spines. 



The first three pairs of legs are prehensile. On the third i):nr (tig. 

 26) there is one spine oti the ischium, six on the nierus. two on the 



Fig. 24.— Frontal lamina and pedix- 

 cle.s of both pairs of antenn.« of 

 jega. quadratasinus. x 9|. 



Fig. 2.'i. — Terminal segment 



WITH I'ROPODA OF -EGA yl'AD- 

 RATASINl'S. X .=>}. 



