352 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxiii. 



elliptical and widely separated, the first one carrying a pair of good- 

 sized lateral lobes. Genital segment subquadrangular, with short 

 and acute posterior lobes. Abdomen two-jointed, the basal joint the 

 larger; anal laminae large, each armed with four plumose setse. Ap- 

 pendages as in the female: all the swimming legs biramose, the first 

 three pairs of rami two-jointed, the fourth pair one-jointed. 



(Gangliopus, yayyXiov, a tumor or swelling, and Trovg, foot, 

 swollen-footed.) 



Neither of these forms has been seen since Gerstaecker first de- 

 scribed them, and there are several points with reference to their 

 anatomy which need explanation. 



In the female the exopod of the first swimming legs is represented 

 as one-jointed and the endopod as two-jointed. But the arrange- 

 ment of the spines on the exopod shows clearl}^ that it is at least a 

 fusion of two joints. And a more careful examination of fresh mate- 

 rial would probably show that it is imperfectly segmented; accord- 

 ingly it has been given here as two-jointed. Again, Gerstaecker says 

 that the abdomen of the female is two-jointed, and that the basal 

 joint carries at its posterior corners two oval laminae. Such append- 

 ages are not found on any Caligid, but their interpretation becomes 

 easy if we regard them as rudimentary legs like those in Dinematura. 



Wliat he calls the basal joint of the abdomen will thus become 

 the sixth thorax joint, well separated from the genital segment as in 

 several other species. He does not mention any dorsal plate for this 

 sixth segment, but such a plate might be easily overlooked when it 

 was concealed between the genital segment and abdomen. The simi- 

 lar plate which exists in Echthrogaleus has escaped detection up to 

 the present time. 



For the male nothing is said in the text about the swimming legs 

 and all information has to be taken from the figure given, which, 

 however, does not show either the first or second pairs. Accordingly 

 we have to fall back upon the supposition that these are the same 

 as in all the Nogaus species or Gerstaecker would have noted the 

 difference. This method is not very scientific, but it is all we have at 

 present. 



Genus PKRISSOPUS Steenstrup and Liitken. 

 Perissopus dentatus, Steenstrup and Lutkbn, 1861, p. 393, pi. xii, fig. 25. 

 Female. — Carapace wider than long, narrowed anteriorly; poste- 

 rior lobes short, sometimes almost lacking. Frontal plates narrow 

 but distinct, with a broad and well defined median incision. Eyes 

 three in number, placed nearly in a row, the middle one the smaller. 

 Three free thorax segments, each with a pair of dorsal plates, the 

 first pair lateral and oblique, the second median and nearly hori- 

 zontal, the third the largest, extending entirely across the body. 



