106 THE VOYAGE OF H.M.S. CHALLENGEK. 



(magnified 50 diameters), e,y from Station No. 122 (magnified 60 diameters) ; PL XVIII. 

 fig. 4, a-f, figures a-d, from Station No. 246, e, f, from Station 300 (magnified 50 

 diameters).] 



7G. Cythere circumdentata, n. sp. (PL XXVI. fig. 2, a-c). 



Valves, seen laterally, oblong, subquadrangular, rather higher in front than behind, 

 height equal to half the length ; anterior extremity weU rounded posterior rounded below, 

 angular at its junction with the dorsal margin ; dorsal margin straight, ventral sinuated in 

 the middle, the whole circumference of the shell strongly but irregularly dentated. The 

 outline, as seen from above, is exactly similar to that of Cythere dasyderma. Surface of 

 the valves beset with deep polygonal fossse, and round the marginal portions with 

 numerous short spines. Length, l-24th of an inch (1"05 mm.). 



This comes very close to Cythere dasyderma, and may, perhaps, be but an extreme 

 form of that species ; it is, however, somewhat larger, more oblong in shape, has a surface 

 sculpture composed of larger pits, and is only sparingly spiniferous, except near the 

 margins. Detached valves were found in two dredgings only; in lat. 36° 10' N., long. 

 178° 0' E., 2050 fathoms (Station 246), and in lat. 13° 28' S., long. 149° 30' W., 2350 

 fathoms (Station 276). 



[PL XXVI. fig. 2, a-c. a Left valve (Station 276) seen from outside, h the same from 

 above, c left valve (Station 246) seen from above. AU magnified 40 diameters.] 



77. Cythere suhmi, n. sp. (PL XXVI. fig. 3, a-h). 



Carapace of the female, seen from the side, subquadrangular, scarcely higher in front 

 than behind, height equal to nearly two-thirds of the length ; extremities rounded and 

 beset, somewhat sparingly, with spines of irregular length ; dorsal and ventral margins 

 nearly straight, the former irregularly indented and spinous ; seen from above, the shell 

 is about twice as long as broad, widest in the middle, the lateral margins extremely con- 

 vex, converging with a gentle curve towards the front, but very abruptly behind, the 

 extremities forming very large and broad, truncated prominences, armed with divergent 

 terminal spines ; the hinder portion of the central mass bears also several stout backward- 

 pointing spines ; end view irregularly five-sided ; the elevated central portion of the valves 

 is limited in front and behind by a flattened zone which forms, when seen from the dorsal 

 or ventral surfaces, two strong terminal projections, the margins (except the ventral) are 

 irregularly spinous and the general surface is vaguely undulated. Length, l-24th of an 

 inch (1"95 mm.). 



Only one perfect specimen and a few separated valves of this fine species have been 

 seen. These occurred in a dredging from lat 35° 41' N., long. 157° 42' E. ; 2300 

 fathoms (Station 241), and off" Prince Edward's Island, 50 to 150 fathoms. The valves 

 figured at 4, a, h, which at one time I took to belong to Cythere suhmi probably belong 



