REPORT ON THE OSTRACODA. 90 



66. Cythere sidcatoperforata, n. sp. (PL XXVI. fig. 1, a-d). 



Valves, seen from the side, subquadrangular, nearly equal in height throughout, height 

 equal to two-thirds of the length ; anterior extremity boldly rounded ; posterior nearly as 

 broad as the anterior, produced in the middle ; dorsal margin elevated into a gibbous 

 prominence at each end, between which points it is irregularly spinous ; ventral margin 

 convex, slightly sinuated in front and dentated behind ; seen from above, the outline of 

 the sheU is ovate, with dentated margins ; the end view has its sides broken with two 

 deep angular excavations, corresponding with two longitudinal furrows which run nearly 

 the whole length of each valve. The shell-surface is sculptured with numerous scattered 

 subangular fossse, arranged in interrupted, more or less longitudinal, rows. Length, 

 l-23d of an inch (I'l mm.). 



Only one or two detached valves of this species were found in a dredging from 1375 

 fathoms, Lit. 33° 42' S., long. 78° 18' W. (Station 300). 



[PL XXVI. fig. 1, a-d. a Left valve seen from side, h from above, c from below, 

 d from front. Magnified 40 diameters.] 



67. Cythere dictyon, n. sp. (PL XXIV.. fig. 1, a-y). 



Shell of the female, seen from the side, oblong, subquadrangular, not much higher in 

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

 rounded, fringed below the middle with numerous short teeth ; posterior subtruncated, 

 scarcely rounded, irregularly toothed on the lower half; the dorsal margin slopes gently 

 from before backwards, and is always, in adult specimens, more or less u-regularly 

 jagged, while in some cases (figs. _;' and v) the indentations are remarkably deep ; ventral 

 margin more or less convex ; seen from above, the outline is lozenge-shaped or somewhat 

 hastate, about twice as long as broad, sides subparallel or converging gently towards the 

 front, extremities broad and truncated ; end view subtriangular, with convex margins and 

 rounded angles. Shell-surface covered with an irregular network of ribs, the main lines 

 of which have often an obscm-ely radiate arrangement, originating in an obsolete central 

 tubercle ; just within and parallel with the ventral margin is a prominent, sharply-cut 

 ridge, which is often produced behind the middle of the valve into a strong spine, but is 

 continued in a less prominent style round the anterior and posterior portions of the shell, 

 thus enclosing an elevated central area. The shell of the male is shown at figures e-g, 

 and has usually a more strongly developed spinous armature than is seen in the female. 

 Length, l-25th of an inch (1 mm.). 



I have thought it desirable to figure more copiously than usual some of the more 

 remarkable forms, as well as various stages of growth, of this widely-distributed and 

 variable species. Many intermediate varieties might have been added to those given in 

 the plate, but a careful examination of these figures will, I think, be sufficient to show 

 pretty conclusively the unity of the series. The ventral ridge is conspicuous even in the 



