114 



THE VOYAGE OF H.M.S. CHALLENGER. 



straight, or very slightly convex and sub-parallel ; seen from above, the outline is ovate, 

 tapering with a gentle curve towards the front and more suddenly behind ; the anterior 

 extremity is obtusely pointed, the posterior broader and deeply emarginate ; width only 

 a little less than the height ; end view subcircular. Surface of the shell perfectly smooth 

 and polished, marked sometimes with a few scattered circular papilla, and in old speci- 

 mens becoming of an opaque milky or yellowish-white. Length, l-34th of an inch 

 (75 mm.). 



I have memoranda of the occurrence of this species off Christmas Harbour, Kerguelen 

 Island, in a depth of 120 fathoms (Station 149); and off the Ki Islands, 580 fathoms 

 (Station 191). 



2. Krithe producta, n. sp. (PI. XXVII. fig. 1, a-j). 



Carapace of the female more flexuous and more tumid than that of Krithe hartonensis ; 

 seen from the side, subreniform ; greatest height situated in the middle, and equal to 

 more than half the length ; anterior extremity rounded off, posterior oblique, rounded off 

 above and obscurely angulated below ; dorsal margin moderately arched, ventral sinuated 

 in the middle ; seen from above, ovate, widest in the middle, width equal to half the 

 length, pointed in front ; posterior extremity wide, truncate, and centrally emarginate ; 

 sheU-surface quite smooth, or beset with numerous minute closely-set punctures and a few 

 distant circular tubercles. The shell of the male (figures e-g) is much narrower and more 

 elongated, and has its ventral and dorsal margins almost straight. Length, l-34th of an 

 inch ("75 mm.). 



This species is either a cosmopolitan one, and very variable as to shape, or the figures 

 given under its name in PL XXVII. fig. 1, h-j, which are fairly representative of many 

 different examples, must belong to other undescribed species. I prefer, however, to con- 

 sider them as forms of Krithe producta, the variations observable in a large series of 

 specimens being almost countless, and, as I think, in many cases fairly referable to 

 differences of age, sex, or race. This, hoAvever, may be doubted in such a case as that of 

 the valve represented at j, which is not only very remarkable in shape, Ijut is also very 

 much larger than the normal forms of Krithe producta. 



Specimens which, for the present at least, must be held to belong to this species 

 occurred in the following dredgings : — 



Lat. 38° 25' K, long. 35° 50' W., 

 „ 38°ll']Sr., „ 27° 9'W., 

 „ 28° 42' N., „ 18° 6' W., 

 „ 8° 37' S., „ 34° 28' W., 



Off North Brazil, 



Off Prince Edward's Island, 



Lat. 46° 46' S., long. 45° 31' E., 



Off Sydney, 



