410 
CLATJSA. 
Figijees. 
PI. XIIT. Pig. 15. A branch, X 10 clia. MidcUe Chalk: 
Chatham. Vine Coll. D. 2711. 
PI. XVII. Pig. 11. A branch of var. obliqua, in which the 
radial ribs are faintly visible in only the lower part; X 10 dia. 
Middle Chalk : Chatham. Vine Coll. D. 699. 
Pig. 55. A longitudinal section, X 9 dia. Scnonian — Coniacian : 
Luynes. D. 4649. 
Pig. 55 . — Clausa heteropora (Orb.). Longitudinal section. 
{d — dactyletbra'.) 
Afpinities. 
This species is the earliest of the genus Claicsa^ and the typical 
forms of it come from the Cenomanian ; but a practically identical 
form is common in the Craie de Yilledieii and Craie marneuse of 
Touraine. In d’Orbig-ny’s original figures of his E. punctata and 
A*, obliqua the zoarium is represented as strongly punctate ; but 
this appears to have been an error of the artist, for the surface 
is described as smooth when perfect, and as otherwise showing 
“les cellules avortees” and not pores (p. 896). 
Pergens includes the C. heteropora as a synonym of Claviclausa 
clava and Cavea elongata ; but the Museum specimens and 
d’Orbigny’s figures render it probable that the last names are 
synonymous, and refer to a species of Petalopora ; whereas 
C, heteropora is a true Clausa, with regular, spiral apertures. 
It would be better to adopt the name obliqua, as the variety is 
commoner than the Cenomanian type, but the name heteropora 
has prior claim, dating from the “ Prodrome ” ; its original 
description is no doubt inadequate, and it can only be recognized 
