38 



J. F. Fitzpatrick, Jr. 



Mi. 



ou 



r L *. 



^o^t^ 



sr 



Gulf of Mexico 



Fig. 8. Distribution of Fallicambarus (excluding F. uhleri). Arrow as in Figure 

 1. Horizontal rulings = F. byersi; vertical rulings = F. oryktes; stippling = F. 

 danielae; enclosed by open circle = F. hortoni. 



Fallicambarus oryktes (Penn and Marlow) is found in the Florida 

 Parishes of Louisiana and along the Mississippi coast. Its eastern limits 

 abut the western limits of the morphologically and ecologically distinc- 

 tive F. byersi (Hobbs). The latter taxon probably represents more than 

 one species, but this does not interfere with the geographic interpreta- 

 tions; the populations occur as far east as the Yellow River basin in 

 Florida. As does F. oryktes, it (they) occurs in the immediate vicinity of 

 the coast, rarely penetrating more than 100 km inland. Fallicambarus 

 danielae Hobbs is similarly distributed, but apparently it is geographi- 

 cally sympatric with the respective extremes of the two earlier-mentioned 

 species in the central part of the coast. Thus, the spread of these taxa 

 seems to be an event of the late Pliocene or early Pleistocene (Fig. 8). I 

 am not prepared here to discuss the factors that led to establishment of 

 other species of the genus, except to note that the genus and at least 

 some species probably are the result of pre-Pliocene events. 



Faxonella probably began in the environs of central Louisiana, 

 where one finds the greatest diversity and the apparently most primitive 

 forms. Indeed, only Fx. clypeata (Hay) is widely distributed, and it is 

 found restricted to post-Eocene areas of Alabama and Mississippi in 



