Vol.51.] EADIOLA.RIAN ROCKS IN THE LOWER CULM MEASURES. 639 



Order DISCOIDEA, Haeckel. 



Genus Theodiscus, Haeckel. 



Test a simple lenticular latticed shell, with three marginal 

 spines. 



Theodiscus aculeatus, sp. nov. PI. XXVI. fig. 3. The test is now 

 partially crushed ; originally it seems to have been somewhat oval 

 in outline; the diameter is - 2 mm. The three marginal spines are 

 unequal in length ; the longest measures - 5 mm., and •04 mm. in 

 thickness at the base ; there are also some smaller spines. Traces 

 of lattice-structure are shown. This form is allied to Th. gigas, 

 Rust, from the Silurian of Cabrieres ('Pala3ontographica,'vol. xxxviii. 

 1892, p. 163, pi. xx. fig. 4) ; the test is slightly larger ; the spines 

 are longer but less robust. Not uncommon at Rarashorn Down. 



Genus Sethodisctjs, Haeckel. 



Test consisting of a lenticular latticed cortical shell connected by 

 radial beams with a simple medullary shell, and having the margin 

 of the circular disc simple. 



Sethodiscus chudleighensis, sp. nov. PL XXVI. fig. 13. Only a 

 vertical section of this form has been recognized. The cortical test 

 is lenticular, -15 mm. in length, and '09 mm. in breadth ; the 

 inner test is circular in outline, *05 mm. in diameter, and it is con- 

 nected with the outer test by numerous radial beams. Within the 

 smaller test are several rods, which radiate from an excentric point 

 to the margin. From the hedge-section at Lawell House, Chud- 

 leigh. 



Genus Lithocyclia, Ehrenberg. 



Test discoid, with a lenticular latticed cortical shell connected by 

 radial beams with a simple medullary shell surrounded by one 

 or more concentric chambered equatorial rings, without radial 

 appendages. 



Lithocyclia devoniensis, sp. nov. PI. XXVI. fig. 4. The test, as 

 shown in section, is elliptical ; the long diameter is *23 mm., the 

 lenticular shell is "115 mm., and the central chamber "065 mm. 

 There are four rings ; the inner one is somewhat wider than the 

 others. The radial beams are only faintly shown. Ramshorn 

 Down, Devon. 



Genus Trigonocyclia, Haeckel. 



Test discoid, with lenticular latticed cortical shell, simple medul- 

 lary shell, and three solid radial spines on the margin of the disc. 



Trigonocyclia ? sp. a. PI. XXVI. fig. 11. Test triangular in out- 

 line, two sides nearly straight, the third slightly curved, with long 

 stout spines from the angles. Diameter of disc '2 mm. ; length of 



