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



35. Cytliere wyville-thomsonl, n. sp. (PI. XX. fig. 4, a-f). 



Shell of the female, seen from the side, oblong, quadrangular, highest over the 

 anterior hinge-joint, the height being equal to more than half the length ; anterior 

 extremity boldly rounded, fringed from above the middle with a series of small and 

 regular serratures ; posterior truncated, produced below the middle, and bearing four or 

 five short, very stout and blunt spines ; dorsal margin elevated over the anterior hinge, 

 thence sloping steeply, and with two or three abrupt sinuations, backwards to the 

 posterior extremity, where it is sharply angulated ; ventral margin straight ; seen from 

 above, the outline is very irregularly hastate, fully twice as long as broad, the lateral 

 margins deeply indented in the middle, converging gently in front and abruptly behind, 

 and forming at each extremity a wide truncated prominence, the hinder one cut up 

 into a number of blunt spines ; end view irregularly triangular ; the margins of the 

 valves, as in the preceding species, are much expanded, and marked by transverse lines ; 

 the hinge-tubercles are large and prominent, the central portion of the valves has a 

 large round elevated tubercle, while within the ventral and, less distinctly, also near 

 the dorsal margin runs a sharply-cut longitudinal ridge, these ridges being especially con- 

 spicuous on the dorsal and ventral aspects of the shell ; the general surface of the valves, 

 including the lateral tubercle, is thickly sculptured with angular excavations. Length, 

 l-28th of an inch ('9 mm.). 



A fine series of this very well marked species was obtained in the clredgings 

 from Balfour Bay and Christmas Harbour, Kerguelen Island (Station 149). It occurred 

 also in those from lat. 52° 4' S., long. 71° 22' E., 150 fathoms (Station 150) ; off Heard 

 Island, 75 fathoms (Station 151) ; Torres Straits (?), lat. 11° 35' S., long. 144° 3' E., 155 

 fathoms (Station 185). 



PL XX. fig. 4, a-f. a Shell of female seen from left side, h from above, c from below, 

 d from front, e male seen from left side, /from above. All magnified 40 diameters.] 



36. Cy there par allelogramma, n. sp. (PL XV. fig. 1, a-e). 



Carapace, seen from the side, oblong, quadrangular, nearly equal in height through- 

 out, the height being less than one-half the length ; anterior extremity obliquely rounded, 

 and sometimes obscurely dentated below the middle ; lower half of the posterior margin 

 slightly rounded and minutely dentated, upper half obliquely truncated (in the right 

 deeply excavated); dorsal margin almost straight, terminating behind in a produced 

 angle, ventral straight ; seen from above, the outline is oblong, ovate, with irregularly 

 sinuated sides. The surface of the valves is marked throughout with coarse, irregularly 

 shaped excavations ; within the anterior and ventral borders runs a more or less distinct 

 elevated ridge, aiid just in front of the middle of each valve is a large, rounded tuber- 

 cular elevation, the markings of which are smaller than those on other parts of the shell. 

 Length, l-30th of an inch (-85 mm.). 



