PKOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 351 



and somewhat expanded distally, where it is fnlly a third as broad as 

 long ; the digital portion is very slender, nearly as long as the basal 

 portion, nearly straight to the slender, acnte, and chitinous tip which is 

 strongly eurved, and the prehensile edge is thin and very minntely ser- 

 rate. The dactylus is almost exactly of the same form as the digital 

 portion of the propodns, and its prehensile edge is armed in the same 

 way, bnt the cilia npon the onter edge are much longer than on the cor- 

 responding part of the propodns. 



The third and fourth ])airs of pera^opoils are successively a very little 

 shorter than the second and have very nearly the same form. From the 

 coxal to the meral segment they are very nearly as stout as in the second 

 pair, but the three distal segments are much more slender. The basal 

 part of the i^ropodus is subcylindrical and only very slightly expanded 

 and tlattened distall,^•, while the digital part and the dactylus are equal 

 in length, very slender and weak, straight throughout, without incurved 

 or chitinous tips, and densely ciliated along the i:)rehensile edges. 



The fifth or last pair of perteoi)ods (figure 4) are considerably shorter 

 and more slender than the fourth, aud all the segments except the pro- 

 podns and dactylus have very nearly the same relative proi)()rtions as 

 in that pair. The basal i)ortion of the propodns is a little longer than 

 the cari)us, subcylindrical a>nd slightly tapering distally ; the digital 

 portion is about as long as the proximal thickness of the proixxlus, very 

 slender, and tapers to a rounded tii>. The dactylus is fnll^^ twice as long 

 as and much stouter than the <ligital part of the pro]>odus, and straight 

 and subcylindrical. 



As seen from above tlie sides of the pleon are nearty straight, and 

 form, with the telson, a regular acute triangle. The first five segments 

 are carinated dorsally, aud the carina projects forward from cacli seg- 

 ment in an acute tooth, but the carina and tooth are small and low on 

 the first segment, increase rapidly to the fourth, wl)ile on the fifth they 

 are scarcely as prominent as on the fourth, and on the sixth the carina 

 is inconspicuous and there is no tooth, but the top of the carina is 

 traversed by a narrow longitudinal sulcus. On the first segment there 

 are, in addition, two slender si)ines each side projecting forward above 

 the articulations with the carapax. The dorsal surfixce of tlie i)leon, 

 «nther side of the median carina, is smooth and scarcely at all sculptured, 

 bur ah)ng the lateral margin, where the pleura bend abruptly and nearly 

 perpendicularly downward, there is a series of deep longitudinal sulci, 

 except upon the narrow first segment, which is unsculptured, and upon 

 the sixth, where the sulcus is replaced by a simple carina. Of the 

 pleura themselves, the first is nearly obsolete, the second is broader 

 than deep, projecting back over the third with a broadly rounded mar- 

 gin, and forward in a prominent but rounded angle, and has a central 

 circular depressed area ; the succeeding pleura decrease regularly in 

 size posteriorly, scarcely overlap when the abdomen is extended, are 

 convex in outline posteriorly but straight or slightly concave anteriorly, 



