GBNEEA UEOTHOE AND UEOTHOIDES. 3 



Lower antennm. Peduncle spinous ; the flagellum in the male very long, and multi- 

 articulate, in the female very short, two-jointed ; calceoli present in the adult male 

 both on the flagellum and on the last joint of the peduncle. 



First and second gnatliopods similar, subchelate, the wrist larger than the hand ; the 

 finger of the first gnathopod longer than that of the second, each having a little 

 transparent cap over the tip. 



First and second perceopods having the third joint longer than the strongly spined 

 fourth or fifth. 



Third perceopods with the first, third, and fourth joints dilated, the third, fourth, 

 and fifth strongly spined, and furnished with long plumose setae; the fourth joint 

 as wide as or wider than the third. 



Fourth perceopods the longest, with long plumose setae on the first and third joints. 

 In all the perceopods the finger has the inner margin more or less nodulous or serrulate 

 and has a cap over the tip. 



Pleopods having the inner ramus conspicuously shorter than the outer, and in the 

 female tlie peduncle distally widened. 



Third ui^opods. The outer ramus furnished with a small second joint. 



Telson in general cleft nearly to the base. 



Body generally obese, not much either depressed or compressed ; the side-plates not 

 very large. Gland-cells are distributed in great numbers over different parts of the 

 animal. 



In this genus the eyes are very variable ; in some, if not in all, species the eyes, 

 though very large in the male, are of moderate size in the female, and very small in 

 the young. In Urothoe ahhreviata, Sars, no eyes were observed ; but the specimen being 

 very small and probably young, it cannot be inferred with certainty that this is a blind 

 species. The second joint of the mandibular palp forms an angle or bend near its 

 base, owing to which its full length is sometimes not perceived. The inner plate of 

 the first maxillae appears to be always slender and slightly curved ; the first joint of the 

 palp seems to vary in its proportion to the second, to which it is sometimes equal, 

 while in other cases it may be longer or shorter than it. Boeck has remarked that, 

 when Dana attributed to this genus long and narrow maxillipeds with very small inner 

 lamellae, he was thinking only of his Urothoe rostratus, which belongs elsewhere. 

 Spence Bate was perhaps influenced by Dana's account when describing the oiiter 

 plates as small, and the inner as rudimentary; they are, in fact, both of moderate 

 size. In most, and perhaps in all, species the wrist of the first gnathopod is distin- 

 guished from that of the second by having a' row of short feathered setae planted just 

 within the distal margin. As a rule, there is an oblique row of setae on the outer 

 surface of the third and fourth joints of the first and second peraeopods ; long feathered 

 setae are attached to the inner distal margin of the third and fourth joints and to the 

 inner surface of the fifth joint in the third perceopods, also to the inner surface of the 



b2 



