442 DESCRIPTION OF [Puli/gastrica. 



interior ; entire (not perforated) at the ends ; sculptured, and forming 

 a cylindrical smooth tubule. 



Tliis genus approaches nearest Bihlarium, which is allied to Tessella, 

 but free ; Bihlaria are compressed and angular j Stylohiblia are 

 rounded, and have a peculiar internal structure. The present genus 

 has also an affinity with the obscure genus Hemizoster (which should 

 perhaps be cancelled) by its cylindrical figure, but differs in having 

 its surface sculptured. 



STYi,OBiBLrcrM Clypeus. — Lateral valves orbicular, sculptured, with 

 15 to 20 radiant lines, three or four of which are often continuous 

 at the middle; cylinders made up of 34 lamina (valves or leaflets). 

 Diameter of valve 1- 792nd. Possil. Oregon and Siberia. 



S. dwisum. — Lateral valves orbicular ; area of disc occupied with 

 generally ten Hnes, interrupted by a clear large linear space at the 

 centre. Diameter 1 -600th. Fossil in Oregon. 



S. eccentricum. — Lateral valves orbicular, loosely sculptured, with 

 5 to 7 eccentric curved lines, not broken (divided). Diameter l-760th. 

 A fragment of a cylinder contained nine leaflets. Fossil. Oregon. 



Some forms of Bihlarmm Rhoinhus possess almost an orbicular 

 figure. 



Genus Symbolophoea. (Ehr.) — Lorica of two equal valves, orbicu- 

 lar, not in chains, with incomplete cells and septa, the latter radiating 

 a solid angular centre, surface not cellular. 



Sijmholophora differs from Actinoptyclms, by all its cells being in- 

 complete, by the centre being larger, more indistinct, and not cir- 

 cular, and by the surface of the valves being neither cellular nor 

 granular, but occupied by very fine radiating lines. 



S. Trinitatis.—W\t\\. a remarkable crystalline triangular umbilicus, 

 crenulate on its margin, angles rounded, the rest of the disc 

 occupied by six bundles of very fine radiant lines diverging from the 

 centre to the margin. Diameter l-216th. (P. 14, f. 36.) Maryland. 



S. acutangiila- — Very close in habit and size to S. Trinitatis, but 

 its central area (umbilicus) with acute angles. Fossil in Virginia. 



S. (?) microtrias. — Turgid ; disc with very finely dotted rays ; um- 

 bilicus stellate, smooth ; with three narrow rays. Diameter 

 l-48()th. Antarctic Ocean. 



