830 THE VOYAGE OF H.M.S. CHALLENGEK. 



head in this species favours the view taken by Gerstaecker in jihicing the genus among 

 the Phoxina, Sp. Bate (see p. 582). 



Genus Platyischnopus, n. gen. 



Mandibles with denticulate mohir tubercle, third joint of the slender palp elongate. 



First Maxilla} with one-jointed palp, apical spines of the outer plate almost smooth. 



Second Maxillie with the plates broad, especially the outer. 



Maxillipeds with the outer plate reaching bej'ond the second joint of the palp, and 

 having long teeth on the inner margin. 



Both pairs of Gnathopods long and slender, with the first, second, and fourth joints 

 lone, and the hands chelate. 



The Fourth and Fifth Perieopods with the third and fourth joints of great breadth, 

 and carrying numerous spines. 



Tlie Telson emarginate. 



The head long, irregularly-shaped, produced over ])oth pairs of antennai to a rostral 

 tip ; none of the side-plates deep. 



The generic name is derived from the Greek words, TrX-aru?, Ijroad. tcrx^o's, narrow, 

 TTou?, a foot, and refers to the union in the animal of very narrow with very broad 

 feet. 



The general structure brings the genus into alliance with the subfamily Phoxinae, 

 Spence Bate, as defined by Boeck, while the perseopods show a relationship to those of 

 Urothoe and Haustorius (Lepidactylis), so that it may stand for the present in the 

 family Pontoporeiidse, although the combined characters of its peculiar head, the chelate 

 gnathopods, and the emarginate telson, give it a more or less isolated position among 

 the Amphipoda at present known. 



Platyischnopus mirahilis. n. sp. (PI. LVIIL). 



Head long and remarkable, the short rostral peak in our specimen puckered 

 perhaps accidentally, behind this the head widens rather aljruptly, and continuing to 

 widen forms a tract included in the back of which are the first joints of the peduncles of 

 the upper 'or front antenna3; close behind these the head becomes quite abruptly shallower 

 and then again deepens gradually to the base, the eyes occupying the shallow part 

 between the places of insertion of the upper and lower antennas ; the dorsal line of the 

 head is nearly straight, longer than the first three segments of the peraBon united; of the 

 perajon- segments the sixth and seventh are the longest, and the seventh has the postero- 

 lateral angles acutely produced to a small extent ; of the pleon-segments the first has the 

 posterodateral angles rounded, the second has these angles acute, the third acute and 



