212 
Z0NATULID2E. 
Affinities. 
This genus is a near ally of Plethopora, hut differs by the 
arrangement of the mesopores in bands, alternating with the 
apertures, instead of in raised groups or tufts. The walls of 
the zooecia are strongly moniliform. 
The genus has often been confused with Zonopora^ the type 
species of which is Zonopora spiralis, a species that has also been 
used as the type of Spiroclausa. Zonopora^ however, has cork- 
screw-shaped stems with bands of zooecia, separated by bands of 
dactylethrae ; Hamm’s institution of the genus Zonatula was 
therefore a useful step. 
The most primitive species of this genus is the IN’eocomian 
Z. cottaldina, in which the apertures are in verticils around the 
stem ; from this species there is a gradual passage to Z. irregularis, 
in which the complete circle of apertures is broken up into two 
regular, alternate, wedge-shaped groups. In the Albian Z. lavigata 
these wedge-shaped groups are altered into irregular alternate 
bands. 
Zonatula differs from Multizonopora by the lamellar structure 
of the zoarium in the latter genus. 
1. Zonatula pseudotorquata (von Hagenow), 1851. 
Synonymy. 
Flethopor a pseudotorquata, von Hagenow, 1851. Bry. maastr, Kr, p. 45, pi. v. 
%. 9. 
,, ,, AViukler, 1864. Mus. Teyl., Cat. Pal. IBt. ii. p. 208. 
Zonopora ,, d’Orbigny, 1854. Bry. Cret. p. 29. 
,, TJbaghs, 1879. Descr. Geol. Pal. Limb. p. 225. 
,, ,5 Ubagbs,. 1888. C.E,. Excursion: Bull. Soc. beige 
Geol. vol. i., Mem. p. 233. 
Zonatula ,, Hamm, 1881. Bry. mastr. Ob. -Sen. i., Cycl. p. 38. 
Ceriopora kraepelini, Pergens, 1894. Xouv. Bry. Cret. Limb. : Bull. Soc. beige 
Geol. vol. vii., Mem. p. 177, pi. x. figs. 1, la. 
Diagnosis. 
Zoarium dendroid, with thick, cylindrical, dichotomous, and 
sometimes anastomosing branches. The apertures occur in 
bands, separated by narrow bands of mesopores along con- 
strictions of the stem. 
The bands of mesopores are arranged in a spiral groove in the 
