REPORT ON THE RADIOLARIA. 945 



deer. If the lateral ends of the branches of this species become united in the frontal plane, we get 

 Microciibiis, the four upper spines forming the mitral ring, the four middle the equatorial ring, and 

 the four lower the basal ring. 



Dimensions. Diameter of the gate O08 ; length of the spines 0'09. 



Habitat. Central Pacific, Station 272, surface. 



7. Lithocircus furcatus, n. sp. 



Gate ovate. King ovate, with three sharp prominent edges. The two lateral edges are smooth, 

 The median edge (in the sagittal plane) bears sixteen to twenty forked spines (commonly eight 

 dorsal, eight ventral, and four basal). All the spines are of nearly equal size, slightly curved, and 

 about half as long as the short sagittal axis of the ring. 



Dimensions. Diameter of the gate 0'08 to 012 ; length of the spines 0'03 to 0'04 



Habitat. North Pacific, Station 253, depth 3125 fathoms. 



8. Lithocircus magnificus, n. sp. (PI. 81, fig. 16). 



Gate ovate or nearly elliptical. King ovate, with three prominent edges, and numerous richly 

 branched spines arising from the three edges. The specimen figured, which I observed living in the 

 Mediterranean, exhibited eight bunches of larger spines, three dorsal, three ventral, one apical, and 

 one basal bunch ; the latter much larger than the seven others. Each bunch was composed of two 

 to four larger and numerous smaller spines, their branches curved and forked. The ovate purple 

 central capsule, with a distinct podoconus, filled more than the half of the gate. 



Dimensions. Diameter of the gate 01 to 013 ; length of the spines 0'05 to 015. 



Habitat. Mediterranean (Portofino, 1880), Atlantic (Canary Islands), Station 354, surface. 



Genus 403. Zygocircus, 1 Biitschli, 1882, Zeitschr. f. wiss. Zool.,, vol. xxxvi. p. 496, 



Definition. Stephanida with a simple dipleuric or bilateral ring, smooth or 

 thorny, without branched spines and basal feet. 



The genus Zygocircus and the following Dendrocircus differ from the two preceding 

 older genera in the bilaterally symmetrical or dipleuric form of the sagittal ring. Whilst 

 in Archicircus and Lithocircus the two sagittal halves or bows of the ring, the dorsal 

 and ventral bow, are equal (therefore the fundamental form amphithect or diphrag- 

 matic), here both bows become distinctly different ; the dorsal bow is constantly more 

 straight (often vertical), the ventral bow more convex (obliquely ascending). This 

 dipleuric differentiation is most important, as it is transmitted to the greater number 

 of NASSELLABIA by heredity. 



1 ZygocirciiA = Yoked or symmetrical ring ; vyti>, x/jxoj. 

 (ZOOL. CHALL. EXP. PAST XL. 1886.) Rr 119 



