178 
CEISIXA. 
the older regions must be due to lateral gi’owth, so that the 
character appears useless. In any case ‘ Crisina disticha' (Groldf., 
2 Jars) must gi'ow laterally, and would differ only from the Chalk 
lleticrisincE by being less laterally compressed. 
The latter are probably deep-sea allies of Reticrisina disticha. 
1. Crisina (Reticrisina) obliqua (d’Orbigny), 1850. 
Synonymy. 
ReticuHpora obliqua, d’Orbigny, 1850. Prod. Pal. vol. ii. p. 264. 
,, ,, d’Orbigny, 1851. Bry. Cret. pi. 610, tigs. 1-5, fig. 6? 
,, ,, d’Orbigny, 1853-4. Ibid. p. 906, pi. 768, figs. 1, 2. 
,, ,, Brauns, 1875. Sen. Salzb. : Zeit. Ges. Naturw. vol. xlvi. 
p. 401. 
,, ,, Pergens, 1890. Revision, p. 355. 
,, ,, Pergens, 1893. Bry. St. Pat. : Bull. Soc. beige Geol. 
vol. vi. p. 205. 
Diastopora reticulata. Vine, 1884. Fourth Report : Rep. Brit. Assoc. 1883, 
p. 168. 
Diagnosis. 
Zoarium an iiTegular network, consisting of a crowded seiies 
of radial pinnate branches. The branchlets are opposite and project 
distally, and unite with the branchlets of the adjacent branches. 
The posterior surface is flattened and the general aspect is regular ; 
but owing to the irregular vertical growth the anterior surface 
appears irregular and often imeanchiform. 
The meshes are flamboyant, lanceolate, hexagonal, or irregular. 
Zooecia small and veiy numerous. The number of apertures in 
a vertical series ranges from nine (excluding young and immature 
branchlets) to more than forty. 
Dimensions. 
Fide Pergens. B.M., D. 3954. 
Thickness of branch — ... 1 ram. 
Height of branch £-7 mm. ... 4-5 ,, 
Diameter of zooecia -16 ,, ... •2-'3 ,, 
Diameter of aperture *07 ,, ... ‘1--25 ,, 
Distance of series of peristomes ... — ... •4-'7 ,, 
Disteieution. 
England : 
Upper Chalk : Sussex ; near Maidstone ; Dover ; Beachy Head. 
Middle Chalk : Chatham. 
