814 THE VOYAGE OF H.M.S. CHALLENGEE. 



homologically not the front but the lower margin ; the hand is constructed and armed on 

 the same plan as in the first pair-, but is of enormously greater breadth, exceeding the 

 breadth of the side-plate as well as its own length ; it is rather wider at the palm than at 

 the rounded base, and the incision in the palm-margin near the palmar spine is very 

 deep ; the size of the finger matches the requirements of the increased palm. 



First Perwopods. — Side-plates evenly oblong, armed as in the preceding pairs. 

 Branchial vesicles as with the preceding pair, but rather larger. First joint reaching but 

 little beyond the side-plate, with some very long setaj on the lower part of the convex 

 hind margin ; the second joint short, the third long, broad, as long as the fourth and 

 fifth together, with setse on the hind, and apex of the front, margin ; fourth joint oval, 

 narrower distally than at the base, shorter but broader than the fifth joint, the hind 

 margin fringed with long setaj and carrying at the apex a long thick spine, nearly equal 

 in length to the fifth joint ; the fifth joint slender, of nearly even width throughout, 

 fringed with setse on the hind margin and carrying four stout spines of different lengths 

 near its apex ; the finger not half the length of the fifth joint, of unimportant appearance 

 among the neighbouring spines. 



Second Peraeopods. — Side-plates very broad, a little deeper than broad, excavation 

 behind descending a very small distance, lower margin carrying setse as in the preceding 

 segments, joining the hind margin with a gentle curve. First joint not reaching the end 

 of the side-plate ; details of the limb similar to those of the preceding pair. 



Third Perseopods. — Side-plates much broader than deep, hind lobe narrower but 

 deeper than the front one. Branchial vesicles broadest above, forming a triangle with 

 the neck at one corner of the base. The first joint broadest above, almost oval, but that 

 the front margin is nearly straight ; the setse along this are short at the upper and long 

 at the lower part of it, the hind margin is almost entirely smooth and unarmed ; the 

 second joint short ; the third not long, broad, with setse along most of the front margin, 

 spines and setse at and near the apex behind ; the fourth equal in length to the third, a 

 little less broad, with setse on both margins, various groups of spines on the front and at 

 the apex of the hind margin ; the fifth joint longer and thinner than the fourth, the 

 armatui'e of the same character ; the finger more than half the length of the fifth joint, 

 more like a great spine than a joint, at the tip curved a little forward, near the some- 

 what thickened base carrying two dorsal cilia, one feathered in the usual way, the other 

 pectinate with long teeth. 



Fourth Perseopods much longer than the third or fifth. Side-plates very shallow, 

 much broader than deep. First joint broadly oval, with numerous and long setse on the 

 convex front margin, the hinder almost unarmed ; the third joint subequal in length to 

 the fifth, with spines and setse on both margins ; fourth joint a little shorter, with setse 

 on the hind margin, spines on the front, and apex of the hind, margin ; fifth joint slender 

 and straight, with spines and setse on the hind, spines on the front margin, an apical 



