Table 1. — Elementary statistics for samples of 

 Panopeus obesus (N = 209) and P. simpsoni (N = 

 200) from Mobile Bay, Ala; measurements in mm. 



able for subspecific status. After field observations in 

 southwestern Alabama, it was apparent that the two 

 forms which she recognized in that area differ 

 markedly from each other, although no obvious 

 external feature will distinguish every individual. 



Color 



There is a difference in the dorsal coloration of liv- 

 ing animals, P. obesus being generally russet in tone 

 whereas P. simpsoni is mottled gray. The chelae of P. 

 obesus exhibit a "veined" pattern over the external 

 surface of the palm whereas those of P. simpsoni are 

 mottled brown, gray, and yellow-white, fading to 

 cream color ventrally. The inner surface on the 

 ischium of the third maxilliped bears a large, prox- 

 imal red spot in both male and female P. obesus. The 

 color of this spot is persistent in fluids which are com- 



TABLE 2. — Regression statistics for samples of Panopeus obesus and P. simpsoni from Mobile Bay, Ala.; 

 measurements in mm. First variable of each pair is independent (x). 



pairs of attributes except for the slope of carapace 

 length:body depth, but the Y-intercepts of those two 

 lines differed significantly. 



A number of other characters compared in pre- 

 liminary tests are not included in this discussion 

 because they provided minimum information for 

 defining differences between P. obesus and P. 

 simpsoni. These characters included statistical com- 

 parisons of the fifth pereopods of dactyl and pro- 

 podus lengths, third maxilliped ischium and merus 

 widths, major chelae, dactyl lengths and widths, fron- 

 tal and frontoorbital widths, and shape of male 

 gonopods. 



Conclusions 



Rathbun (1930) considered forms of the mud crab, 

 Panopeus herbstii, s.L, to be distinct but unaccept- 



TABLE 3.—F statistics for results of ANCO VA comparing measured 

 characters from samples of Panopeus obesus and P. simpsoni from 

 Mobile Bay, Ala 



' = significant at P= 0.05. 

 " = significant atP= 0.01 

 NS = Not significant. 



monly used for preserving study specimens, although 

 it may fade after periods of storage. Males of P. 

 simpsoni possess this spot but females lack it. 



Morphometry 



Panopeus obesus is a wider, deeper bodied form 



889 



