REPORT ON THE RADIOLARIA. 509 



Genus 221. Stylodictya, 1 Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. 



Berlin, p. 54. 



Definition. P orodiscida with numerous (five or more, commonly eight to 

 twelve) solid radial spines, regularly or irregularly disposed on the margin of the 

 circular or polygonal disk ; margin simple, without a porous equatorial girdle. 



The genus Stylodictya comprises the majority of this subfamily, in which the 

 number of the marginal spines exceeds four. Commonly we find eight to twelve 

 spines, more or less regularly disposed (four perradial and four interradial, or four 

 perraclial and eight adradial) ; but often also the number and disposition become 

 irregular (sometimes veiy large). In my Monograph (1862, pp. 495, 515) I had 

 separated the concentric disks with closed circular rings (as true Stylodictya, s. str.) 

 from the spiral disks with convoluted rings (Stylospira). But I retain these two 

 groups here only as two subgenera, as intermediate forms between them are very 

 common, and often a part of the disk concentric, a part spiral (compare above, p. 492). 



Subgenus 1. Stylodictyon, Haeckel, 1862, Monogr. d. Radiol., p. 495. 



Definition. All rings of the disk concentric, commonly circular (rarely a little 

 elliptical or polygonal). 



1. Stylodictya gracilis, Ehrenberg. 



Stylodictya gracilis, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 28. 



Stylodictya gracilis, Ehrenberg, 1873, Monatsber. d. k. pruuss. Akad. d. Wiss. Berlin, p. 257; 



Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxiii. fig. 3. 

 Stylodictya gracilis, Haeckel, 1862, Monogr. d. Radiol., p. 499. 



All rings of the disk concentric, circular, of equal breadth (the first ring sometimes, but not 

 constantly, four-lobed). Pores regular, circular, small, three on the breadth of each ring. Four 

 perradial beams (crossed in two perpendicular diameters) beginning from the circular central 

 chamber, four interradial beams from the first or second ring (sometimes others between them). 

 Beams prolonged into eight to twelve (or more) marginal spines, bristle-shaped, as long as the radius 

 of the shell. 



Dimensions. Diameter of the disk (with four rings) 012 ; breadth of each ring 0'013 ; 

 pores 0-0025. 



Habitat. Fossil in Tertiary rocks of Barbados and Nicobar ; living in the depths of the Pacific 

 and Atlantic. 



1 Stylodictya = y!et with styles ; orvho;, lixrvti/. 



