PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 351 



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

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

 jiortion, nearly straight to the slender, acute, and chitinous tip which is 

 strongly curved, and the prehensile edge is thin and very minutely ser- 

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

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

 way, but the cilia u]ion the outer edge are much longer than on the cor- 

 responding part of the propodus. 



The third and fourth pairs of peraeopods 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 propodns is subcylindrical and only very slightly expanded 

 and flattened distally, 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 prehensile edges. 



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

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

 podus and dactylus have very nearly the same relative proportions as 

 in that pair. The basal portion of the propodus is a little longer than 

 the carpus, subcylindrical and slightly tapering distally; the digital 

 j)ortion is about as long as the proximal thickness of the propodus, very 

 slender, and tapers to a rounded tip. The dactylus is fully twice as long 

 as and much stouter than the digital part of the propodus, and straight 

 and subcylindrical. 



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

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

 are carinated dorsaliy, and the carina projects forward from each seg- 

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

 the first segment, increase rapidly to the fourth, wliile 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 sjtines each side projecting forward above 

 the articulations with the carapax. The dorsal surface of the pleon, 

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

 but along the lateral margin, where the jfieura bend abruptly and nearly 

 peri)endicularly downward, there is a series of deep longitudinal sulci, 

 except upon the narrow first segment, which is unsculi)tured, 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 ])leura decrease regularly in 

 size ]X)steriorlj', scarcely overlap when the abdomen is extended, are 

 convex in outline posteriorly but straight or slightly concave anteriorly, 

 and the third, fourth, and fifth are ornamented with a median curved 



