22 BRITISH FOSSIL CORALS 
1. Favra minutissima, Duncan. PI. VII, figs. 9—11. 
The corallum is encrusting, gibbous, and small. 
The calices are very small, close, and with very scanty intercorallite tissue. 
There are twelve septa. 
The cost are continuous. 
Diameter of the calices, under 7th inch. 
Locality. Waldon. Jn the Collection of the Geological Society. 
This is the smallest of the Pavia. 
Division—AstREACER. 
Genus—THAMNASTR&A. 
THAMNASTRA#A SuPERPOSITA, Michelin, sp. Pl. VII, figs. 13—17. 
MM. Milne-Edwards and Jules Haime thus notice this species (‘ Hist. Nat. de 
Corall.,’ vol. 11, p. 559) : 
““M. Michelin’s specimen is very young; it is encircled by a strongly folded epitheca, 
which is formed of two layers. 
“No columella is distinguishable. 
“The septa are tolerably strong and unequal. 
“There are three cycles, with the rudiments of a fourth in one or two systems.” 
The superposition of the calices is remarkable, and I cannot but place a Coral found 
in the Irish Upper Greensand by Ralph Tate, Esq., F.G.S., in this species. 
Locality. Ireland; Upper Greensand. In the Collection of R. Tate, Esq., F.G.S. 
