ART. Vll.-A SYNOPSIS OF THE NORTH AMERICAN SPECIES OF 

 THE GENUS ALPHEUS. 



r.^ 



By J. S. KiNGSLEY. 



The materials upon which the following paper is based are the col- 

 lections of the Peabody Academy of Science at Salem, Mass., and of the 

 Peabody Museum of Yale College at New Haven, Conn., which latter 

 were kindly loaned the writer by Prof. S. I. Smith. 



ASTACUS (pars), Fabricius, Entomologise Systematicoe, 1793, ii. 478. 



Pal^mon (pars), Oliver, Encyclopedie Mdthodique, 1811, v. 656. 



AxPHEUS, Fabricius, Suppl. Ent. Syst. 1798, 404. — Latreille, Genera Crustac^s et Insec- 

 torum, 1806, i. 52; id. Considerations G^ndrales sur . . . les Crustac^s, etc. 

 1810, 101. — Say, Journal Academy Natural Sciences, Philadelphia, 1818, i. 243. — 

 Bosc, Hist. Nat. des Crustac^s, 2e ^d. par Desmarest, 1830, ii. 72. — Gray, iu 

 Griffith's Cuvier, Crustacea, 1832, 192. — H. Milne-Edwards, Hist. Naturelle des 

 Crustac6s, 1837, ii. 349. — Dana, U. S. Exploring Expedition, Crustacea, 1852, 

 i. 534, 541.— Bell, British Stalk-eyed Crustacea, 1853, 270. 



Bet^us, Dana, op. cit. i. 534, 548. — Stimpson, Proceedings Acad. Nat. Sciences, Phila. 

 delphia, 1860, 31. 



The genus Alpheus, as limited by the writer, is characterized by 

 having a compressed form, the carapax being extended forward, form- 

 ing a hood over the eyes, the rostrum either small or wanting; the an- 

 tennulae with a two-branched flagellumj antennse with a large antenna! 

 scale. Mandible deeply bifurcate, the anterior branch being oblong, 

 slender ; a man4ibular palpus present ; external maxiliipeds are slender^ 

 of moderate length ; hands of the first pair generally greatly enlarged, 

 unequal, sometimes the right and sometimes the left being the larger in 

 the same species. The second pair are slender, filiform, chelate, the 

 carpus multiarticulate. The remaining feet and the abdomen present no 

 characters of especial importance. 



In 1852, Dana characterized the genus Betceus, which differs from 

 Alpheus, as accepted by him, merely in the absence of a rostrum and the 

 inversion of the hands, the dactylus being borne on the lower edge of 

 the propodus. That the line separating these two genera cannot be 

 drawn is shown by the fact that Betceus trispinostis Stm. is rostrated, 

 while in a large series of Alpheus minus Say I found many which 

 wanted the rostrum. The hand also cannot be taken as a guide, for we 

 find forms of Alpheus heterochelis, in which the dactylus is a little in- 

 clined; in my Alpheus cylindrieus, it works still more obliquely, while in 

 my Alpheus transverso-dactylus its motion is in a horizontal plane. Thus 



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