72 CALIFORNIA ACADEMY OF SCIENCES. 



three pairs of legs slender; merus imarmed. In the male the first and 

 second abdominal segments are free, the third, fourth and fifth coalesced^ 

 second and third joints transversely ridged and produced laterally into 

 two acute processes which project beyond the margins of the other seg- 

 ments; sides of the fourth segment strongly convex; last segment narrow 

 and shorter than the preceding one. In the female, the second and third 

 joints are much like those of the male; fourth and fifth transversely 

 ridged, fifth and sixth of subequal length; last joint very small and 

 triangular. 



Length of carapace, male 25.25 mm. 



Breadth of carapace, male, between tips of lateral spines. . .53 mm. 



Length of cheliped, male 66 mm . 



Length of hand male 35 mm. 



Another specimen measured 26 mm. by 52 mm. 



South America (Milne-Edwards), West Mexico, Pan- 

 ama (Milne-Edwards), Cape St. Lucas (Stimpson), San 

 Diego! Santa Catalina Island! San Pedro! 



The specimens of Amphitrite paucispinis which were 

 sent by Lockington to Streets and Kingsley were, I 

 believe, wrongly identified with Stimpson's Achelous 

 panamensis, instead of with A. Xantusii Stimpson, to 

 which species I feel sure they belong *. Judging from 

 Stimpson's descriptions, Xantusii and panamensis are 

 closely allied, the latter species being distinguished by the 

 presence of a spine on the merus of the ambulatory legs. 

 Streets and Kingsley state that Lockington's specimens 

 agreed very well with Stimpson's description of pana- 

 mensis, except that the spine on the merus of the ambulatory 

 legs was absent. I have examined some of Lockington's 

 specimens of Amphitrite paucispinis, which are in the 

 possession of the California Academy of Sciences, and 

 they agree perfectly with Stimpson's description of 

 Achelous Xantusii, and A. Milne-Edwards' excellent 

 figures of that species in the " Mission Scientifique au 



i See Bull. Essex Inst., Vol. IX, p. 107. 



