406 Mr. E. J. Micrs o?i some 



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 setaj ; 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 Porcellanella (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 antennal joint is very long and the eyes minute, 

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

 cheles, Gibbes, it maybe distinguished by the equal size of the 

 chelipeds and the serrate edges of the fingers. 

 San Francisco, Sept. 5, 1878. 



XLV. — On a small Collection of Crustacea made hy Major 

 Burton in the Gulf of Ahaba. By Edwaed J. MiERS, 

 F.L.S. &c. 



The Crustacea collected by Major Burton are not numerous, 

 including but nine species in all, and belonging, with one 

 exception (the cirripede Tetraclita porosa), to the Decapoda. 

 All are well-known forms ; but their examination gives the 

 opportunity of bringing together under one head certain nomi- 

 nal species which have long been regarded on insufficient 

 grounds as distinct, on which account the synonyma have been 

 cited more fully than would otherwise have been necessary. 

 It is of interest to note that the few species collected by Major 

 Burton in this narrow gulf at the northernmost extremity of 

 the Red Sea are, with one exception [Ocypode cegyptiaca)^ 

 forms whose geographical range extends as far eastward as 

 the islands of the Pacific. 



