136 PROCEEDINGS OF THE ACADEMY OF flggO 



u 



Histoire des Crustaces et de la Insects, vi, p. 27, " An. XI " (1803-4.) 

 Uca Leach, Trans. Linn. Soc, London, xi, p. 309 (1815). Gelasimus 

 Latreille, Nouvelle Dictionnaire d'Histoire Naturelle, xii, p. 517 

 (1817) ; Henri Milne-Edwards, Histoire Naturelle des Crustaces, ii, 

 p. 49 (1837) ; Annales des Sciences Naturelles, III serie, xviii, p. 

 144 (1853) ; Dana, Crustacea of the United States Exploring Expe- 

 dition, pp. 312 and 315 (1852) ; Hess, Archiv fiir Naturgeschichte, 

 xxxi, Pt. II, p. 145 (1865); Alphonse Milne-Edward.s, Nouvelle 

 Archives du Museum d'Histoire Naturelle, xi, p. 271 (1873) ; 

 Oonoplax (pars.) Lamarck, Histoire Animaux sans Vertebres, v. p. 

 353 (1818). 



The genus Oelasimus belongs to Cyclometopa {Ocypodoidea of 

 Dana), family Macrophthalniidse (Dana), and sub-family Ocypo- 

 dinae of the same author. It is characterized by the rhomboidal 

 carapax, broader in front, the elongate ocular pedicels, the eyes 

 proper being placed at the extremity, and by the great inequality 

 of the chelipeds in the male. 



In my studies I have found the characters derived from the 

 larger cheliped of the male to be the most constant, vrhile the 

 I'elative proportions of the carapax, the front and the margins of 

 the orbit, are of but slight importance and very variable. 



But two species ever referred to this genus b}'^ authors, are 

 now^ referred to other genera ; Gelasimus cordiformis forming 

 the type of the genus Helcecius of Dana, and Gelasimus tel- 

 escopicus Owen, which belongs to the genus Macrophthalmus. 



The genus may be divided into two groups, possibly of sub- 

 generic value, according as the front between the eyes is wide or 

 narrow, and the wide fronted section again according as the male 

 abdomen is seven or five jointed. 



§ A. Front very narroiv between the eyes. 

 1. Gelasimus maracoani Latreille. PI. is, f. 1. 



Ocypoda maracoani Latreille, Hist. Crust, et Ins., vi, p. 46 (1803). 



Oelasimus maracoani luAtveiWe, Did. A^Wxst. Nat., xii, p. 519 (1817); 

 Desmarest. Coneid. (pars) p. 133 (1835); Edw., Hist. Nat. Crust., 

 ii, p. 51 (1837) ; Ann. Sci. Nat., Ill, xviii, p. 144, pi. Ill, f. 1 (1852) ; 

 Dana, U. S. Ex. Ex, Crust., p. 318 (1853) ; White, List. Crust. Brit, 

 Mus., p, 85 (1847). Gonoplax maracoani Lamarck, Hist. An. 

 Sans Vert., v, p. 354 (1818). Oelasimus armatus Smith, Trans. 

 Conn. Acad., ii, p. 133, pi, ii, f, 5, pi. iii, f. 4 (1870) ; Report Pea- 

 body Acad. Sci., iii, p, 91 (1871). 



Regions distinct, each branchial ornamented with a longitudinal 

 ridge, from which branch off smaller ones. Ischium of larger 



