DESCRIPTIONS OF TWO NEW PARASITIC ISOPODS 

 BELONGING TO THE GENERA PALzEGYGE AND PRO- 

 BOPYRUS FROM PANAMA. 



By Harriet Richardson, 

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



A number of specimens representing a new species of Palsegyge 

 and four specimens representing a new species of Prohopyrus were 

 collected in 1911 by Dr. S. E. Meek and Mr. S F Hildebrand at 

 Panama and the Canal Zone, during a biological survey of the Isthmus 

 of Panama under the auspices of the Smithsonian Institution. The 

 specimens were found parasitic on Macrobrachium acanthurus and 

 M. jamaicense as well as on the young of the latter or M. olfersii. 



PALSEGYGE MEEKI, new species. 



Body of female ovate, somewhat asymmetrical. Length, 9 mm.; 

 width, 7 mm. Color of dorsal surface white, with a few lines of black 

 along the median line and on either side about halfway between the 

 median line and the lateral margins. Incubatory lamella3 on one 

 side covered with black lines; on the other side only the first one is 

 covered, the others having a few black lines at the base. 



Head large, 2 mm. long and 2 J mm. wide, deeply set in the thorax; 

 anterior margin widely rounded with the antero-lateral angles pro- 

 duced in small acute lobes. Eyes absent. (See fig. 1.) First two 

 segments of thorax short in the median dorsal line and about equal 

 in length; the following five segments are much longer in the median 

 line and are subequal. Epimera are present on the first four seg- 

 ments, occupying the anterior two-thirds of the lateral margin. 

 Ovarian bosses are also present on these segments and are placed on 

 the anterior part of the sublateral margin. On the last three seg- 

 ments the epimera occupy the entire lateral margin. 



All six segments of the abdomen are distinct. The sixth or terminal 

 segment has a posterior incision which extends half the length of the 

 segment, forming two posterior lobes. There are five pairs of double- 

 branched pleopoda, a pair for each of the first five segments, making 



Proceedings U. S. National Museum, Vol. 42— No. 1914. 



521 



