CRUSTACEA. 

 76 



Macropodinea and part with the Maiinea. The three ^nera in *+ 

 form a' natural group, as is at once ob V1 ous on sligl Urn k c m A 

 new crenus, Oregonia, from the Oregon coast, is so closely related to 

 Eu y ; diu , that but for the penult joint of the eight postenor legs 

 L/lould'fbrm the same genus; vet the leg, , m <***^»^ 

 long but the species under a different relationship might Mm With 

 the Maiinea. This disposition to give high importance to the mere 

 length of the legs was so strong in earlier authors, that on this ground 

 mainly Hynienosoma was formerly united with the Inachidae. 



It seems obvious, therefore, that in this threefold subdivision of the 

 Maioidea, too much stress is laid on a mere variation of length m a 

 single set of organs. This is especially true of the first two groups. 

 The third is a more natural association of genera, and is borne out by 

 other characters. There is a like objection to the basis on which De 

 Haan has separated the Inachus group (in which Edwards's Macro- 

 podinea are included, excepting Latreillia and Doclea). His distinc- 

 tion rests on the third joint of the outer maxillipeds — a part liable to 

 important variations even in the same genus; the Inachus group having 

 this joint articulated with the fourth by its summit, and the other 

 Maioidea, by the inner apex. But while Eurypodins exemplifies the 

 former, Oregonia is an instance of the latter, and thus his character 

 divides widely these related genera, In fact, Eurypodins is not essen- 

 tially different in this respect from Oregonia. The articulation takes 

 place with the same part normally in both, and this is true in other 

 genera of the Inachus group. 



The Maiinea and Macropodinea, therefore, properly form but a 

 single group. The genus Latreillia, however, is excluded, as done by 

 De Haan; its outer antennae being moveable and cylindrical to their 

 base, its inner antennas without fossettes, its vulvae in the base of the 

 third pair of legs, and the dorsal position of its hind legs, show a close 

 relation to Dromia and Dynomene. Oncinopus has similar outer an- 

 tennas, and prehensile legs behind, but these legs are not dorsal, and 

 the vulvas are in their normal position. This genus forms a group by 

 itself, distinct from the true Maiinea. 



The grand divisions of the Maioidea, are therefore, as follows : — 



Legio I. Maiinea. — Corpus saspissime oblongum. saepius antice 

 augustum et rostratum. Articulus antennarum externarum Imus sub 

 oculo insitus, anteriusque productus, testa externa sine sutura ooafes- 

 cens. Pedes forma normales. 



