DESCRIPTIONS OF TEN NEW ISOPODS. 



By Pearl L. Boone, 

 Aid, Division of Marine Invertebrates, United States National Museum. 



The 10 new species herein described are accumulations from vari- 

 ous collections of Isopods transmitted to the United States National 

 Museum. 



The one new genus, Pterisopodus, is so widely different from all 

 previously known forms of the suborder Cymothoidea that it has 

 been necessary to establish a new family for it, the Pterisopodidae. 



The illustrations were made by Mrs. E. Bennett Decker, under 

 my direction. 



Suborder GNATHIDIE. 



Family GNATHIIDAE. 



GNATHIA TRIOSPATHIONA. new species, 



Plate 91, fig. 3. 



Male. — Body elongate, 2.9 mm. wide, 8.8 mm. long, head and 

 thorax of nearly uniform breadth, about 2.8 mm.; abdomen quite 

 narrow, 0.9 mm., gradually tapering posteriorly. Head large, sub- 

 quadrangular, dorsal surface deeply carinated; a median dorsal 

 groove-like depression divides the head into two lobes; this depres- 

 sion widens anteriorly forming a deep V-shaped excavation, enhanc- 

 ing the bilobed impression ; below this depression the frontal margin 

 is produced triangularly into a rostral process with a tooth-like pro- 

 jection on either side of the median point; the frontal margin of each 

 supraocular lobe is recurved, having a tricrenulate aspect. The 

 superior antennae have a peduncle of four stout, subequal articles, 

 and a flagellum of four short, fine articles, and extend to the flagel- 

 lum of the inferior antennae; the inferior antennae have a peduncle 

 of four unequal articles and a flagellum of eight small articles, and 

 are one and one-half times as long as the mandibles. The eyes are 

 elongate-oval, composite, moderately large, and placed in the extreme 

 anterolateral margins. 



The mandible is 2 mm. long with the outer margin a smooth, 

 thickened ridge, broad at the base and decidedly tapering toward 

 the tip which is acutely incurved; the inner margins are produced 

 into three distinct blades — a superior, which is very narrow and 



Proceedings U. S. National Museum, Vol. 54— No. 2253. 



591 



