130 THE VOYAGE OF H.M.S. CHALLENGER. 



The remarkably ventricose character, and broadly triangular end-view separate this 

 species unmistakably from any other with which I am acquainted. 



[PL XXX. fig. 3, a-cl. a Carapace seen from left side, 6 from above, c from below. 

 d from front. Magnified 60 diameters.] 



13. Xestoleberis foveolata, n. sp. (PL XXX. fig. 1, a-g). 



Carapace of the female, subcordate, very tumid; seen from the side, the greatest height 

 is situated near the middle, and is equal to more than two-thirds of the length ; anterior 

 extremity rounded, and only slightly depressed, posterior very broadly rounded, and some- 

 what produced in the middle ; dorsal margin very boldly arched, ventral nearly straight ; 

 seen from above, broadly and obtusely wedge-shaped, tapering rather abruptly near the 

 anterior extremity, which is obtusely pointed, posterior extremity wide, subtruncate, mth 

 rounded angles, and a central submucronate projection ; greatest width situated behind 

 the middle and equal to three-fourths of the length ; end view subtriangular, with 

 extremely convex sides, and rounded lateral angles, apex obtusely angulated, width 

 rather greater than the height. Surface of the shell ornamented with closely-set, and 

 rather large angular excavations, and, on the ventral surface, also with deep longitudinal 

 furrows. Length, l-45th of an inch (-53 mm.). The male diff'ers from the female in 

 having the superior margin almost angular in the middle, the dorsal view being regularly 

 ovate, and the end view subtriangular. 



This remarkable species, differing from all other known members of the genus in the 

 strongly pitted character of its shell, was dredged plentifully in a depth of 6 to 8 fathoms, 

 off Booby Island, lat. 10° 36' S., long. 141° 55' E. (Station 187). 



[PL XXX. fig. 1, a-g. a Carapace of female seen from left side, 6 from above, c 

 from below, d from front ; e male seen from left side, / from below, g from front. 

 Magnified 60 diameters.] 



Cytherura,G. 0. Sars (1865). 



Valves unequal and dissimilar in form, the right more or less overlapping the left on 

 the dorsal margin ; surface smooth, reticulated, punctated, deeply excavated, or bearing 

 irregularly disposed ribs or protuberances, and mostly marked with a central darkly- 

 coloured areola ; in shape oblong or subtriangular and produced at the hinder end into a 

 more or less prominent beak ; hinge-processes mostly obsolete. Anterior antenna shortly 

 setose, six-jointed, gradually tapered: second joint bearing a rather long seta on the 

 middle of its posterior margin ; posterior antenna five-jointed, with short terminal claws ; 

 flageUum long, triarticulate. Mandibles robust, bluntly toothed ; palp three-jointed, its 

 branchial appendage small and bearing only two recurved setae. Terminal lobes of the 

 first pair of maxillae long and narrow ; iDranchial plate bearing on its external margin two 

 non-ciliated setse, which are directed downwards and arise from a separate lobe. Feet 



