136 PROCEEDINGS OF THE ACADEMY OF [1880. 



arcuate, but iu the young the}* are parallel or even concave, con- 

 verging behind. Eyes, without st3-liform process, and extending 

 nearly or quite to the orbital angle. Meros of chelipeds with its an- 

 terior margin crenulate in the young, in the adult with spinifonn 

 tubercles. Carpus externally granulate. Hand short, broad, 

 cordate, granulate internally and externally, its lower margin 

 serrate, the stridulating ridge nearly obsolete. Fingers short, 

 compressed, the thumb slightly hooked at the extremity. Meral 

 joints of the ambulatory feet with transverse rugae. Carpal and 

 propodal joints similarly roughened and covered with a short 

 pubescence. 



New Zealand ! Mauritius ! (Guerin) ; Australia ! (E. "Wilson); Sand- 

 wich Is. ! (J. K. Townsend) ; Tahiti] (A. Garrett) ; Mozambique 

 and Zanzibar (Hilgendorf) ; Red Sea, Manilla, Nicobars (Heller) : 

 Hong Kong, Loo Choo (Stm. ) ; Japan (Edw.). 



The following are not true members of the genus : 



0. angulatus Latr. = Gonoplax angulatus. 



0. aurantia Bosc. ex Herbst ^ Thelphusa aurantia. 



0. carnifex Latr. ex Herbst = Cardiosoma carnifex. 



0. hcterochelos Bosc. = Gelasimus heterochelos. 



0. hispana Bosc. ex Herbst = Sesarma sp. 



0. hyJrodromus Latr. ex Herbst == Thelphusa hydrodromus. 



0. longimana Latr. = Gonoplax rhomboidalis. 



0. viaracoani Latr. == Gelasimus maracoani. 



0. macrocheles Bosc. == ? Macrophthalmus sp. 



Q. pugillalor Bosc. = Gelasimus pug illat or. 



O. quadrata Bosc. = Sesama sp. 



0. rufopunctata Latr. ex Herbst = Trapezia rufopunctata. 



0. senex Latr. ex Fabr. = Thelphusa sp. 



0. teirago7ion Bosc. ex Herbst = Gelasimus tetragonon. 

 0. tridens Latr. ex Fabr. = ? Pachygrapsus sp, 



0. vocans Latr. = Gelasimus sp. 



I have not been able to identify 



O. granulata Bosc. (Edit, ii) p. 247. 



0. viacleayana Hess, Archiv. fiir Naturgesch., XXXI, p 143, PI. VI, f. S 



(1865). Australia. 



O. unispinosa Rafinesque, Precis de decouvertes Semiologiques, p. 21, No. 



35 (1814). 



