196 SMITHSONIAN MISCELLANEOUS COLLECTIONS 



antero-lateral margins. The front is tridentate. The antennae are 

 short, as in Remipes. The antennulse are also short, with the in- 

 ferior flagellum very small, almost rudimentary. The external max- 

 illipeds are nearly as in Hippa, with exarthroid palpus ; the apex of 

 the meros- joint is, however, truncated. In the anterior feet the 

 basal or peduncular joints resemble those of Hippa and Remipes, 

 but the terminal joint is flagelliform — that is, long, slender, and 

 multiarticulate. The ambulatory feet and the abdomen resemble 

 those of Remipes, but the external lamella, in the appendages to the 

 penult joint, is much shorter than the internal one. 



304. MASTIGOPUS GRACILIS^ Stimpson 



Pirate; XXI, Fig. i 



Mastigopus gracilis Stimpson, Proc. Acad. Nat. Sci. Phila., x, p. 244 

 [82], 1858. 



Carapax strongly convex in its transverse outline; surface even, 

 but scabrous with asperities, which consist of short transverse im- 

 pressed lines, minutely setose, and most strongly marked anteriorly. 

 Front with three sharp teeth, median one triangular and nearly as 

 prominent as the lateral ones, which are long, slender, and acute. 

 Antero-lateral margin armed with six subspiniform teeth, the an- 

 terior one longest, the rest progressively diminishing. Eyes very 

 long and slender, more than half as long as the antennulse, which 

 are one-third as long as the carapax. External maxillipeds oblong, 

 nearly rectangular, half as broad as long ; their surface fiat and 

 nearly smooth, glabrous, with a few scattered punctse. The basal or 

 peduncular joints of the anterior feet are short, smooth, and nearly 

 naked ; penult and antepenult cylindrical ; terminal segment or flagel- 

 lum longer than the carapax, and consisting of twelve elongated 

 joints, with a ring of long setae at each articulation. Ambulatory 

 feet moderately hairy. Terminal joint of the abdomen lanceolate, 

 thick, with two longitudinal ridges or angles at the base and a deep 

 median sulcus toward the extremity, which is acuminated. The 

 colors in life are as follows : Carapax dark olive, becoming paler at 

 the middle, and brownish at the margins. Front often reddish. A 

 white band crosses the carapax at its posterior extremity. Abdomen 

 bluish, with transverse lead-colored bands at the middle segments. 

 Members all white, with the exception of the external antennae, 

 which are pale blue. Body beneath, white. Length of the carapax 



^ Mastigochiriis gracilis Stimpson. 



