240 E. W. SEXTON. 



tissue of the anterior part of the telson, nearer the dorsal surface. A 

 very fine tube or duct communicating with the exterior rises from the 

 upper surface of the vesicle, on the side away from the median line 

 (Fig. 4 d), while at the bottom of the vesicle, towards the median line, the 

 crystalline bodies of the statolith can be seen (Fig. 5 st). A strong muscle 

 is attached to the anterior wall of each statocyst ; much stronger in 

 Anthura than in Cyathura ; it appears to be attached at its anterior end 

 to the chitin of the telson. This attachment looks like a coloured oval 

 body, and is as noticeable as the statocyst itself, seen in situ (Fig. 2 a), 

 but an examination of the sections shows its construction. The two dotted 

 bodies (Fig. 2 h) are similar muscle attachments in the inner uropods. 



DESCRIPTION. 



Bodij cylindrical, much more stoutly built in the female than in the 

 male, with strongly marked longitudinal keels, three in the female, four 

 in the male. In both sexes there is a dorso-lateral keel on either side, 

 starting in the male just behind the eye, and finishing at the end of the 

 peraeon, while in the female it runs the whole length of the body, from 

 the tips of the lateral angles of the head to the end of the pleon. In both, 

 also, the mid-ventral keel is well developed. The male has, in addition, 

 on the head and peraeon, a smaller but well-defined mid-dorsal keel, 

 most marked on the anterior segments. 



Pleon. In the female the first five segments are coalesced and equal 

 in length to the last peraeon-segment, in the male these segments are 

 distinct and equal in length to the two last segments of the peraeon. 



Head in the female almost square, with a short rostrum and with the 

 anterior lateral angles also produced and projecting a little further 

 forward than the rostrum. In the male the shape is quite different, 

 the front of the head from the eyes tapering gradually downwards to a 

 strong obtuse rostrum (Fig. 1). 



Eyes black, very prominent in the male, and of great size, occupying 

 nearly half the surface of the head and almost meeting dorsally ; om- 

 matidia very large, distinct from each other, corneal facets convex, the 

 whole eye resembling a blackberry. In the female the eyes are much 

 smaller, round in shape, and flat, not prominent. 



Upper Antennae in the female shorter than the lower antennae. The 

 first joint of the peduncle is equal in length to the second and third taken 

 together ; flagellum two-jointed, consisting of one long joint without 

 setae, and a minute terminal joint carrying a cluster of eight to ten setae 



