Vol. 51.]" ON THE OCCURRENCE OF RAIHOLAEIA IN CHALK. 607 



outline, filled with finely granular crystalline calcite. No outer 

 band and no medullary shell. Three thin delicate and rather long 

 spines, one pair opposite and the third spine at right angles to it. 



Diameter -21 mm. Length of spines '23 mm. 



Locality : Royston. Horizon : Melbourn Rock. 



Suborder Discoidea, Haeckel. 



Spumellaria with discoidal or lenticular central capsule (often 

 with radial prolongations, rarely allomorphic) ; with discoidal, or 

 lenticular fenestrated, siliceous shell (often with radial spines or 

 fenestrated arms, rarely allomorphic). Growth reduced or diminished 

 in the direction of one dimensive axis (Haeckel, ' Challenger ' 

 Report, pt. i. p. 402). 



We refer PI. XXII. figs. 8 & 9 to the suborder Discoidea. 

 Similar forms are common in sections of the Barbados rocks, but 

 the absence of all structure makes it difficult to do more than in- 

 dicate the suborder to which we believe them to belong. 1 Length 

 •37 millim. 



Localities : various. Horizon : Melbourn Rock. 



Like Dr. Hinde, we find forms apparently belonging to the sub- 

 order Sphaaroidea, but not described by Haeckel in his ' Challenger ' 

 Report. They are radiolarians with a single spine extending from 

 the surface of the test. To include these Dr. Hinde has instituted 

 a new genus Dorysphasra, and to this we refer the following : — 



Dorysplmra, Hinde. 



PI. XXII. fig. 10 shows a circle filled with dense amorphous 

 calcareous material, or finely granular crystalline calcite, its limit 

 usually well defined. One long, thin, bristle-like spine. 



Diameter variable, "15 to - 22 mm. Length of spine '20 to "35 mm. 



Localities : One of the most common forms at Hitchin, Royston, 

 Luton, Dover, Richmond Well, 702 feet. 



PI. XXII. fig. 11 is very similar to fig. 10, but the single radial 

 spine is much thicker at the periphery of the test and diminishes to 

 a point at the distal end. 



Diameter T7 mm. Length of spine "13 mm. 



Locality : Hitchin Station railway-cutting. Horizon : Melbourn 

 Rock. 



PI. XXII. fig. 12 is circular in sectiou, filled with dense amorph- 

 ous material : its periphery being well marked by minute, clear, 

 calcific crystals. No indications of a medullary shell. A short, 

 strong radial spine, broad at its base, terminating in a point. The 

 minute calcific crystals extend outside the periphery of the circle, 

 and seem to mark the position of small secondary spines. 



Diameter *16 mm. Length of spine "08 mm. 



1 Dr. Hinde, however, writes with reference to these as follows : — ' As regards 

 f or m, I should not hesitate in placing figs. 8 & 9 in the genus Ampkibrachium.' 



