406 Mr. W. N, Lockington on the Porcellanidm. 



ovate, considerably broader than long, regions indistinct ; 

 front entire, straight; no post- or preorbital tooth. 



Chelipeds smooth, shining, equal. 



Meros stout, produced into a prominent lamina distally and 

 anteriorly ; carpus stout, about twice as long as wide, cylin- 

 drical except posteriorly, where there is a deep concavity for 

 the reception of the posterior side of the manus ; manus stout, 

 cylindroidal, fringed anteriorly with long seta? ; fingers short, 

 abruptly hooked at tip, serrated, the dactylus longer than the 

 pollex. 



Ambulatory feet short, smooth, sparsely setose; meros 

 somewhat compressed ; dactyli multiunguiculate. 



Length of carapax 7 millims., width 10. 



Exact locality unknown ; Lower California. 



This specimen, found among some miscellanea of Mr. 

 Fisher's collecting, evidently belongs to Stimpson's new genus 

 Polyonyx^ having the transversely ovate carapax, and entire 

 front, which distinguish it from PorcellaneUa (White), and the 

 multiunguiculate dactyli which characterize both genera. 



The number of unguiculi does not appear to be equal on 

 all the feet, as I counted four or five on the first ambulatory 

 pair, and three only on the two succeeding pairs. 



The first antenna! joint is very long and tlie eyes minute, 

 according to Stimpson's generic description. From P. macro- 

 cheles^ Gibbes, it may be distinguished by the equal size of the 

 chelipeds and the serrate edges of the fingers. 



San Francisco, Sept. 5, 1878. 



