CRISIS A. 
169 
1. Crisina (Tervia) subgracilis, d’Orbigny, 1850. 
Synoxtmy. 
Crisisina subgracilis, d’Orbigny, 1850. Prod. Pal. yoI. ii, p. 265. 
Crisina ,, d’Orbigny, 1851. Bry. Cret. pi. 614, figs. 6-10. 
Idmonea ,, d’Orbigny, 1853. Bry. Cret. p. 738. 
,, ,, Hamm, 1881. Bry. mastr. Ober-Sen. p. 31. 
,, ,, Pergens, 1890. Eevision, p. 345, pi. xii. fig. 2. 
Eeptotubigera ,, Bucaille, 1890. Bry. Cret. 8eine-Inf. : Bull. Soc. Sci. nat. 
Bouen, vol. xxv. p. 510. 
Clavitubigera depressa, d’Orbigny, 1852 and 1853. Bry. Cret. p. 726, pi. 747, 
figs. 1-5. 
Idmonea francorum, Vine, 1893. Eep. Brit. Assoc. 1892, p. 308. 
FiUsparsa pulchella, Marsson, 1887. Bry. Eiig. : Pal. Abb. vol. iv. p. 35, 
pi. iii. fig. 7. 
non ,, ,, Vine, 1893. Compl. Eep. : Eep. Brit. Assoc. 1892, p. 330. 
Diagnosis. 
Zoarium simple or formed of a few narrow branches, which may 
dichotomize once or more. The obverse face of the zoarium 
is weU rounded and convex ; the reverse is flat, and may be 
concave. The branches are sometimes swollen distally (var. 
ClaviUihigera depressa). 
Zooecia aiTanged in alternate pairs or triplets, with an irregular 
series of additional zooecia along the middle line. Peristomes 
well raised and usually reflexed at right angles. 
Dimensions. 
Fide 
B.M.,D.968. 
B.M., D. 526. 
Simple, broad 
Pergens. 
Branched variety. 
variety. 
Diameter of a branch ... *4 mm. 
•6 mm. 
'5 mm. 
Length of a branch ... — 
— 
•4 „ 
Diameter of zooecia ... '12--16 ,, 
... -2 „ 
. -2 „ 
Length of raised 
peristomes — 

. -4--5 „ 
Distance of pairs of aper- 
tures of same side ... •4-’5 ,, 
... -8 „ 
. -4--85 „ 
Diameter of aperture ... ‘08 ,, 
... -14 „ 
•1 M 
Distribution. 
British : 
Upper Chalk : Gravesend ; Bromley. 
Middle Chalk : Chatham. 
