290 Dr. J. W. Gregory — A Revision 



"Radial ridges broad and compact, broken up into short groups 

 or bands. The bands have from 2 to 4 zooecia in breadth. 



Distribution. — England : Inferior Oolite. Foreign : Ba- 

 jocian, Germany and France. 



Genus 3. Theonoa, Laraouroux, 1821. 



Diagnosis. — Theonoidge in which the zoarium is massive 

 and consists either of dense rounded masses of thick incrusta- 

 tions or erect thick fronds. The surface is crossed by the 

 broad well-marked ridges ; the ridges may expand in some 

 species into broad tubular elevations. 



Type species : T. clathrata, Lamouroux, 1821. 



1. Theonoa clathrata, Lamouroux, 1821. 



Theonoa clathrata, Lamouroux, 1821, Expos, m^th. p. 82, pi. Ixxx. 

 figs. 17, 18. 



Diagnosis. — Zoarium dense, massive, roughly spherical ; 

 the surface of the zoarium is broken into ridges, which are 

 short, broad, and blunt j they never rise into high bilaminate 

 sheets. Four or five apertures occur together in one width 

 of a ridge. 



Distribution. — England : Great Oolite {fide Morris) . 

 Foreign : Bajocian, France and Germany ; Bathonian, 

 France. 



2. Theonoa Bowerbanki, Haime. 



Theonoa Bowerhanki, Haime, 1854, Bry. Jur., M^m. Soc. g^ol. France, 

 s6r. 2, t. V. p. 205, pi. x. fig. 3. 



Diagnosis. — Zoarium composed of many erect irregular 

 sheets ; the sheets are tall, irregularly sinuous, and branched, 

 leaving loose funnel-shaped cavities between them. The 

 zoarium is roughly hemispherical in form. 



The radial ridges are long and fairly continuous ; the 

 summits are flat and contain generally 3 or 4 apertures in the 

 width, but in places they expand and contain 6 or 7 in the 

 width ; the ridges occur on both sid^s of the sheets. 



Distribution. — Inferior Oolite, England. 



3. Theonoa distorta (Lamouroux), 1821. 



Tilesia distorta, Lamouroux, 1821, Expos. m6th. p. 42, pi. Ixxiv. fig. 6 



(non fig. 5). 

 Theonoa distorta, Vine, 1883, 3rd Rep. Foss. Polj^z., Rep. Brit. Assoc. 



1882, p. 267. 



