74 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 5 



placed according to the classification proposed by Rathbun (1930), in 

 which Portunus (P.) acuminatus Stimpson is considered a member of the 

 so-called "acuminatus-asper-panamensis group." Reference to the original 

 description of Achelous acuminatus Stimpson ( 1871 ) confirmed suspicion 

 that the abundant species mentioned above was the real acu?ninatus 

 rather than the photographed specimen (40270) upon which Miss Rath- 

 bun based her revised description in the Cancroid volume and her con- 

 cept of acuminatus, asper, and panamensis as possible forms of a single 

 species. 



Especially significant is the fact that the real acuminatus is a small 

 species, the males rarely attaining a size larger than that described by 

 Stimpson (0.5x1.26 inches), while Miss Rathbun's acuminatus, al- 

 though twice the size ( 1.0 x 2.5 inches) , is considered by her as immature. 



Particulars in which the species under consideration compares better 

 with Stimpson's acuminatus than does the male specimen 40270 are as 

 follows : 



( 1 ) The length of the chelipeds of a male specimen of like dimensions 

 with Stimpson's type, no longer extant, is exactly three times 

 the carapace length instead of two and one half. 



(2) The length of the lateral spine is all of two-thirds times the 

 length of the anterolateral margin instead of one half. This 

 length increases proportionately rather than decreases as the 

 specimens approach the size of Miss Rathbun's. 



(3) The length of the merus of the cheliped is greater than the 

 length of the carapace, as described by Stimpson, instead of less 

 in specimen 40270. 



(4) The manus is very slender instead of scarcely less slender than 

 that of panamensis or asper. 



(5) The carpus of the cheliped is thin in confomiity to the slender 

 manus. 



(In connection with the carpus and manus, it seems well to 

 point out that the thickness of the hand may refer either to its 

 width, as seen in dorsal view, or to its height, as seen in frontal 

 view. Not only is the chela of the true acuminatus very slender 

 from above, but its proportionate height to length is 1 :7 in- 

 stead of 1 :3.5 in the Rathbun specimen.) 



(6) The second, fourth, and sixth anterolateral teeth are appreci- 

 ably reduced instead of "only the second and sixth showing any 



