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



[PL XXXV. fig. 8, a, h. a Right valve seen laterally, h the same from above. 

 Magnified 50 diameters.] 



Xiphichilus, Brady. 



Xiphichilus, Brady, Nat. Hist. Trans. Nortlium'berland and Durliam, vol. iii. (1870). 

 Bythoeythere, Norman, British Association Pieport (1868). 



Shell thin and fragile, smooth ; valves compressed, elongated, pointed at both ends, 

 nearly equal ; ventral margins much compressed, forming a flattened, knife-like plate, 

 which is widest behind the middle, and often marked by several transverse hair-like 

 lines ; seen from above, comj)ressed, bifusiform ; hinge simple. Limbs excessively long 

 and slender ; anterior antennse six-jointed and quite destitute of setse ; posterior 

 sparingly setiferous. Mandibles very long and slender, styliform ; palp (?) biarticulate, 

 slender, and terminating in two long setse. Abdomen produced into two long tapering 

 processes. 



1. Xiphichilus complanatus, n. sp. (PI. XXXV. fig, 4, a-d). 



Shell much compressed, elongated ; seen from the side, oblong, subovate, highest 

 behind the middle, height scarcely equal to half the length ; anterior extremity narrow, 

 rounded ; posterior produced in the middle into an acute angle ; dorsal margin boldly 

 arched, highest behind the middle, ventral margin straight ; seen from above, the 

 outline is excessively compressed, somewhat lozenge-shaped, with subacute extremities, 

 greatest width in the middle, and equal to somewhat less than one-fourth of the length ; 

 end view ovate, produced below into a keel-like flange. Surface of the shell j)erfectly 

 smooth. Length, l-33d of an inch ('77 mm.). 



Found in a dredging from Christmas Harbour, Kerguelen Island, 120 fathoms. 



[PL XXXV. fig. 4, a-d. a Carapace seen from the left side, 6 from above, c from 

 below, d from front. Magnified 50 diameters.] 



2. Xipihichilus (?) arcuatus, n. sp. (PL XXXV. fig. 2, a-d). 



Carapace, seen from the side, subarcuate, height greatest in the middle, and equal to 

 rather more than one-third of the length ; extremities subacute ; dorsal margin forming 

 a continuous arch between the two extremities of the ventral margin, with which it forms 

 an obtuse anterior and a subacute posterior angle ; ventral margin rather convex ; seen 

 from above, compressed, ovate, widest in the middle, more than thrice as long as broad, 

 extremities subacute ; end view ovate, broad on the dorsal, and tapering to a keel at the 

 ventral border. Shell-surface quite smooth. Length, l-45th of an inch ('53 mm.). 



This species was observed only in a dredging from lat. 19° 10' S., long. 178° 10' E. ; 

 610 fathoms ; bottom of globigerina ooze. 



