146 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



tint. Basal portion of merus white, distal end of propodus and dactyl 

 cadmium orange. Ventral side light carmine. (Petersen, of a freshly 

 captured specimen from Islas Secas, Panama) 



The white-tipped fingers, white spots on the epibranchial "shoul- 

 ders," and white areas on the merus of the walking legs are character- 

 istic, and are still visible in most specimens after years in alcohol. The 

 vivid dark carmine coloration of the carapace, also characteristic of live 

 specimens, soon disappears with preservation. 



Ecology: Specimens have been taken in the littoral and to a depth 

 of 4 fathoms. The species is usually found associated with corals, but 

 also occurs under stones. A single specimen was recovered from sponge 

 dredged in 1-4 fathoms at Acapulco, Mexico. 



Ovigerous females have been collected in every month from De- 

 cember through July. 



Relationships: Pachycheles biocellatus is extremely close to P. 

 nisei (Stimpson), 1858, an Atlantic species ranging from the Florida 

 Keys to southern Brazil. Careful comparison of large series of both 

 populations may prove them to be conspecific. 



Remarks: Lockington made the following statement in his descrip- 

 tion of Petrolisthes (Pisosoma) biocellatus: "The larger of the two 

 specimens measures barely three centimetres in length." As Glassell 

 (1937) pointed out, "centimetres" in this sentence was undoubtedly 

 an error for "millimetres." Individuals of 3 mm or less would be small, 

 although not necessarily juveniles, and the fact that Lockington de- 

 scribed the anterior margin of the carpus as being "divided into three 

 low lobes" makes it even more probable that his description was based 

 on small specimens. 



Petrolisthes (Pisosoma) gibbosicarpus Lxjckington has not been pre- 

 viously identified with any known species. It is apparent from the 

 description, however, that Lockington's type, a 6 mm female, belonged 

 to the same taxon as the smaller individuals described by him as bi- 

 ocellatus. The International Rules of Zoological Nomenclature, as re- 

 vised at Copenhagen in 1953, require that when two or more species pub- 

 lished in the same paper and on the same date are united to form a 

 single species, the first reviser must select the name of one of them 

 to be used for that species. Accordingly the name biocellatus is hereby 

 selected in preference to gibbosicarpus, because the former name is al- 

 ready established in the literature. 



