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



28 fathoms, mud (Station 189); Humboldt Bay, Papua, 37 fathoms; Nares' Harbour, 

 Admiralty Islands, 16 fathoms. AH these stations, it will be seen, belong to the 

 Malayan or Melanesian Province. 



[PL LXIV. fig. 2, <x-c. a Carapace seen from left side, h from above, c from below, 

 d from front ; e old shell (variety) from left side. AU magnified 50 diameters.] 



8. Cytherella venusta, n. sp. (PI. XLHI. fig. 4, a-d). 



Carapace oblong, cuneiform ; seen from the side, somewhat obliquely quadrangular, 

 height equal to half the length ; extremities nearly equal, the anterior scarcely rounded, 

 somewhat oblique, and obscurely angulated at its junction with the dorsal margin ; 

 posterior obliquely subtruncate ; dorsal margin almost straight for the anterior half of its 

 course, then sloping gently backwards, ventral very slightly sinuated ; seen from above, 

 the shell is oblong-cuneate, widest at the hinder end, the width at that joint being 

 considerably less than half the length ; the posterior extremity is truncated, and has a 

 broad mucronate prominence in the middle, the lateral margins converging very gradually 

 towards the front, which is obtusely rounded and has a couple of minute teeth, one on 

 each valve ; end view regularly ovate. The surface of the shell is smooth, but marked 

 with a very delicately impressed reticulated pattern. Length, l-37th of an inch 

 {'7 mm.). 



This is a very elegant and distinct species, well characterised by its distinctly cuneate 

 shape and reticulated surface. Several specimens of it occurred in a cbedgiiig from 40 

 fathoms depth ofi" the reefs at Honolulu. 



[PL XLHI. fig. 4, a-d. a Carapace seen from left side, b from above, c from below, 

 d from front. Magnified 60 diameters.] 



9. Cytherella crihrosa, n. sp. (PL XXVI. fig. 5, a-d). 



Carapace oblong, rather tumid ; seen from the side, subquadrate, somewhat higher 

 in front than behind, height equal to more than half the length ; anterior extremity 

 broadly rounded, posterior slightly rounded, obliquely subtruncate, and obscurely angular 

 in the middle ; dorsal margin nearly straight, gently sloping backwards, ventral straight 

 or slightly convex ; seen from above the outline is cuneiform, broadest at the posterior 

 extremity, where the width is equal to nearly half the length ; anterior extremity broadly 

 rounded ; lateral margins nearly straight, ending behind in an obtuse angle, thence con- 

 verging abruptly to the posterior extremity; end view broadly ovate. Surface of the 

 sheU destitute of ridges or undulations, but marked with numerous rather large oblong- 

 excavations. Length, l-52d of an inch ('49 mm.). 



Found only off Nukualofa, Tongatabu, 18 fathoms (Station 172). 



[PL XXVI. fig 5, a^d. a Carapace seen from left side, 6 from above, c from below, 

 d from front. All magnified 60 diameters.] 



