330 



A. E. Verrill — Decapod Crustacea of Bermuda. 



form, are even less granulated.* Indeed, the latter are scarcely more 

 granulated than the ordinary form of HicorcU. 



However, the front of *S'. chierea is narrower and more arched than 

 in S. HicorcU ; its lower margin is less sinuous, narrows more toward 

 the ends, and is less turned up at the edge, so that it is less concave 

 above. The orbital notch is not so deep. Still these differences are 

 but slight. The carapace seems to be slightly less convex. The 

 chelae are essentially the same in both, and the carpal joint is 

 roughened in the same way. The merus joints of the pereiopods 

 are about equally flattened in both; the brush of hairs on the under 



Figure 8. — Sesarma cinerea (from Florida), slightly enlarged. Phot. A. H. V. 



side of the last two joints is nearly the same in both, though per- 

 haps a little smaller, and with shorter hairs in iS. cinerea. The 

 differences are so slight that it seems not improbable that S. cinerea 

 is another semiterrestrial race or subspecies that has been derived 

 from /S. HicorcU, under a somewhat different environment. In fact, 

 all those species that live more or less on the dry land or in trees 

 (e. g., S. JRoberti, an arboreal West Indian species) must have been 

 originally derived from amphibious or aquatic species, but the dif- 

 ferentiation has gone farther in some than in others. Doubtless they 

 all go into the sea to breed, and probably they all have similar zoea 

 and megalops larval stages. 



But in the case of the Bermuda forms, it is easy to believe that 

 they have acquired different breeding habits or different breeding 



* In Miss Eathbuii's analytical table of Sesarmce (Synopsis American Sesarmae, 

 Proc. Biolog. Soc. Washington, xi, pp. 90, 91, 1897), the smoothness of the 

 suprafrontal lobes, " smooth or nearly so," is made a diagnostic character for S. 

 Eicordi, while S. cinerea is put in a group having the suprafrontal lobes 

 " tuberculate or granulate, " and in a subgiYuip having them " faintly granulate." 

 The degree of granulation seems to be variable. 



