926 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



joints, and the whole appendage is nearly as long as the last two joints 

 of tlie peduncle in the following pair. 



In the adult male the second antennte have the peduncle massive, its 

 last joint a little longer than the penultimate, the flagellum consisting 

 of l-t-lT joints, many of which widen distally, with minute spines 

 thrust into pi'omincnce. In the female, alread}^ carrying marsupial 

 plates, the antennte, as shown in the figure, are of insignificant size 

 compared with those of the male. The ten-jointed flagellum equals 

 in length the last two joints of the peduncle. 



The mouth organs exhibit no distinctive peculiarity. The palp of 

 the first maxilhe is minute. No trace of a fourth joint could he per- 

 ceived on the palp of the maxillipeds. 



The first gnathopods of the male have the long wrist or fifth joint 

 distally widened, and on the inner side of the spinulose prominence is 

 a pellucid bubble-like tubercle. The sixth joint is shorter, but simi- 

 larly widened, its prominence beset with spinules and capped with a 

 pellucid portion like the bu])ble on the preceding joint. The small, 

 conical finger closes over a shallowly excavate palm, its point reaching 

 but by no means overlapping the clear prominence. In the female 

 the wrist is distally widened, but without special prominence or tuber- 

 cle, while the sixth joint is for some distance parallel-sided, and then, 

 instead of widening, tapers slightly to the insertion of the finger. 

 Like the preceding joint, it has spines on both margins, those on the 

 hinder or inner margin being the more important. 



The second gnathopods of the full-grown male have large oval hands, 

 with the palm ver}^ oblique, beset on both sides with spines, and in the 

 middle slightly flattened, so as to leave a shallow interval when the 

 massive, .strongly curved finger closes, bringing its apex into the pocket 

 at the end of the palm. Near the hinge of hand and finger the palm 

 has a short but rather deep excavation, into which a corresponding 

 prominence of the finger's inner margin neatly fits. This notable 

 feature occurs elsewhere in the Talitrida3, as in Orchestoklea tuhercu- 

 lata Nicolet, Orcliestla tucuTauna Fritz MtiUer, and Orchestia sulenson 

 Stebbing. These stand, it is true, in different genera, but the generic 

 position of the third is obscure, because the female is not 3'et known. 

 It is, however, clearly distinguished from the species now under dis- 

 cussion by the different character of its first gnathopods. With Fritz 

 Miiller's species there are other difficulties, as will appear by the 

 following quotation from his celebrated treatise." Miiller is calling 

 attention to the fact that the development of the sexual peculiarities 

 does not stand still on the attainment of sexual maturity, and proceeds 

 to give instances: 



For example, the younger sexually mature males of Orchestia Tiicurauna, n. sp., 

 have slender inferior antennae, with the joints of the flagellum not fused together, 



« Fiir Darwin, 1864, p. 54; Accurately translated by Dallas under the title. Facts and 

 arguments for Darwin, 1869, pp. 79, 80. 



