216 B GEOLOGICAL SURVEY OF CANADA. 



faintly indicated. The fifth segment is small, and nearly covered 

 each side by the lateral expansions of the fourth. There are two 

 slender submedian spines upon the ventral side of the fifth segment, 

 and there is a similar single median spine on the first segment of the 

 pleon. 



The antennulre are short, the peduncle reaching scarcely beyond the 

 rostrum ; the first segment is stout and about as long as the second and 

 third together, the second is short and stout, and the third, or ulti- 

 mate, about half the diameter of the second but longer than it ; the 

 major flagellum is slender and about half as long as the peduncle ; the 

 minor flagellum is little longer than the first segment of the major, 

 and is apparently triarticulate. The rudimentary antenna is scarcely 

 longer than the first segment of the antennula, but has the penultimate 

 segment elongated to about four times its diameter, while all the other 

 segments are very short. 



The first gnathopods (second maxillipeds) are nearly as in Diastylis, 

 but are very long and slender, and the basal segments are but little 

 stouter than the terminal. The second gnathopods reach a little 

 beyond the tip of the rostimm : the basal segment in each reaches to 

 the antero-lateral angle of the carapax and is very much expanded 

 distally, so that the two together completely close the space between 

 the lateral margins of the carapax ; the inner angle of the distal end 

 projects in a very prominent and acute tooth, and the inner edge is 

 margined with short plumose setas, but the outer surface is smooth and 

 naked like the carapax ; the ischium is very short and fully twice as 

 broad as long ; the merus is about twice as long as the ischium, not 

 more than half as broad, and bears on the middle of its outer margin a 

 very long plumose seta; the three distal segments are very slender, 

 subequal in length, and each is considerably longer than the merus. 

 The tip of the flagellum of the exognath reaches slightly beyond the 

 middle of the basis of the endopod itself. 



The first perseopods are slender and scarcely as long as the second 

 gnathopods, the tip of the carpus not quite reaching the distal end of 

 the basis of the gnathopod ; the ischium is scarcely longer than broad, 

 the merus twice as long as the ischium, and the three distal segments 

 subequal in length and each a little longer than the merus. The tip 

 of the flagellum of the exopod does not reach the extremity of the 

 basis of the endopod. The second perrcopods reach but little beyond 

 the middle of the basis of the first pair, and the exopod is about as 

 long as the endopod. The sternum of the third free segment of the 

 person is broad and greatly elongated to correspond with the lateral 

 portions of the segment, so that the two anterior pairs of perseopods 

 are sej>arated by a considerable space from the succeeding pairs. The 



