﻿PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



by tile 



SMITHSONIAN INSTITUTION 

 U. S. NATIONAL MUSEUM 



Vol. 102 Washington : 1952 No. 3299 



A NEW SPECIES OF COMMENSAL AMPHIPOD FROM A 

 SPINY LOBSTER 



By Clarence R. Shoemaker 



In January 1942 the late E. F. Ricketts, in connection with the work 

 of his Pacific Biological Laboratory, at Pacific Grove, Calif., examined 

 a living spiny lobster Panulirus interrwptus (Randall) at the local 

 fish market. The lobster, which was presumably sent from Santa 

 Barbara, had some amphipods adhering to its pleopods, and six of 

 these were sent to me for identification. I find that these specimens 

 represent a new species. The structure of the peraeopods indicates 

 that they were modified and developed for the purpose of grasping, 

 and the animals appear to have been living commensally upon the 

 pleopods of the lobster. The mouthparts are of the normal type and 

 are not modified in any way, thus indicating that the animal is not 

 parasitic. The specimens are all females possessing partially de- 

 veloped marsupial plates. 



PARAPLEUSTES COMMENSALIS, new species 



Figure 83 



Female. — Head with rostrum rather short and blunt ; lateral lobes 

 rounding ; eye rather large, black, and renif orm. Antenna 1 : Pedun- 

 cular joints short; first joint not twice as long as second; second joint 

 not twice as long as third; flagellum about tvv'ice as long as peduncle 

 and containing 14 joints (an unknown number of terminal joints are 

 missing). Antenna 2: Peduncle short; fourth joint about twice as 

 long as third and equal in length to the fifth ; flagellum a little longer 

 than peduncle and consisting of 13 joints. 



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967610—52 



