56 CALIFORNIA ACADEMY OF SCIENCES. 



Genus Cycloxanthops Rath. 



Front horizontal, produced, and divided by a median fissure into two 

 deep, lamellate lobes, which are truncated and separated from the inner 

 orbital angle by a rather deep fissure. Orbits small, with the superior 

 margin marked by two fissures. The postorbital angle is only slightly 

 prominent and is continuous with the antero-lateral margin, which is 

 strongly curved behind. Basal antennal joint short, but joined at its 

 internal angle to the front; the flagellum is inserted in the inner orbital 

 hiatus. Merus of the maxillipeds subquadrate, the anterior margin not 

 oblique. The abdomen in the male is composed of five free joints. 



Type. — C. sexdecimdentatus (Edw. & Lucas). 



The genus Gycloxanthus was established by Milne- 

 Edwards^ to receive some species of fossil crabs. Find- 

 ing subsequently that this species was a synonym of 

 Zanthopsis M'Coy, Edwards applied the name Gyclo- 

 xanthus, which he considered as having thus become 

 "disponible/^ to an entirely different genus of which he 

 made sexdecimdentatus the typical species.''^ According 

 to the rule, '^ Once a synonym always a synonym," the 

 name Gycloxanthus is no longer available for use. 



Cycloxanthops novem-dentatus (Lock.) 



Xanthodes ? novem-dentatus Lockington, Proc. Cal. Acad. Sci., Vol. VII, 



1877, p. 32. 

 Xantho novem-dentatus Lockington, Ibid., 1877, p. 99. Kin-gsley, Proc. 



Bost. Soc. Nat. Hist., Vol. XX, 1879, p. 153. 

 Gycloxanthus calif or niensis Eathbun M., Proc. U. S. Nat. Mus., Vol. XVI, 



1893, p. 237. 



Carapace wide, flattened, and more or less punctate behind; convex, 

 granular and rugose in front. Median region divided into three well- 

 defined regions by distinct sulci; branchial regions divided by a transverse 

 sulcus arising from the lateral angles. Front horizontal, produced, eden- 

 tate, with the anterior margin nearly transverse, but a little advanced in 

 the center, and divided by a deep, closed, median notch which may become 



1 dans d'Archiac, Hist, des progr. de la geologie, T. Ill, p. 304, K. 



2 Ann. Sci. Nat. (4), T. XX, 1863, pp. 278 and 307. 



