198 Dr. J. W. Gregory — A Revision 



Diagnosis. — Zoarium growing in dense tufts of long slender 

 cylindrical branches ; these dichotomize repeatedly and occa- 

 sionally anastomose. 



Zocecia regularly cylindrical. 



Peristomes slightly raised ; three or four apertures seen on 

 each side of a branch ; peristomial rows very oblique and 

 crowded, and therefore giving the orifices an apparently 

 quincuncial arrangement. At the ends of branches the peri- 

 stomes are irregular and low (form ccespitosa, Lamx. & Mich., 

 non Haime). 



Distribution. — England : Great Oolite and Forest Marble. 

 Foreign : Bajocian, France and Germany ; Bathonian, 

 France. 



4. Spiropora richmondiensis (Vine), 1884. 



Entalophora richmondiensis, Vine, 1884, Polyz. Richmond Boring, 



Quart. Journ. Geol. Soc. vol. xl. p. 791, fig. 3. 

 Terebellaria P increscens, Vine, 1884, ibid. p. 79. 



Diagnosis. — Zoarium of thin bifurcating stems, from 1 to 2 

 millim. in diameter. 



Zocecia numerous, in regular spirals ; below the points of 

 bifurcation the rows of peristomes become less oblique and 

 increase to ten in number ; elsewhere 7 or 8 zocecia can be 

 seen in a single row across one face of the stem ; zocecia are 

 short and cylindrical. 



Peristomes well raised. 



Distribution. — England: Great Oolite. 



5. Spiropora teiragona, Lamouroux, 1821. 



Spiropora tetragona, Lamouroux, 1821, Expos, meth. p. 85, pi. Ixxxii. 



figs. 9, 10. 

 Cricopora tetragona, Blainville, 1830, Diet. Sci. nat. t. lx. p. 386. 

 Entalophora tetragona, d'Orbigny, 1849, Prod. Pal. t. i. p. 318. 

 Bisidmonea tetragona (non Lamx.), Walford, 1889, Bry. Shipton, 



Part I., Quart. Journ. Geol. Soc. vol. xlv. p. 571, pi. xix. figs. 7-9. 

 Spiropora tetraquetra, Lamouroux, 1821, op. cit. p. 47. 

 Cricopora tetraquetra, Bronn, 1835, Leth. Geogn. p. 247. 

 Bisidmonea antiqua, d'Orbigny, 1852, Pal. franc., Terr. cr6t. p. 720, 



pi. 762. figs. 10-12. 



Diagnosis. — Zoarium composed of thick tetragonal- stems, 

 which dichotomize repeatedly but irregularly ; they form a 

 loose tuft. 



Zocecia short. 



Peristomes slightly raised, arranged in alternate horizontal 

 series (as in Idmonea) . On each face of a stem there occur 

 two rows of apertures placed alternately on the left and right 





