706 R. F. TOMES ON THE OOLITIC 
zontal or concave basal wall, which characterizes the latter species, 
it has much thicker septa, which, when entire, spring boldly in- 
wards towards the centre of the calice, their free margins repre- 
senting the segment of a circle, and they pass into the centre, and 
there form a spurious columella. 
In the above-quoted work of MM. Milne-Edwards and Haime, 
the present species (which had been placed by M. d’Orbigny in the 
genus Prionastrea, after the examination of specimens from Bou- 
logne) was doubtfully included in the genus Jsastrea. In their 
later work*, however, it was placed in that genus without any such 
expression of uncertainty. 
BATHYC@NIA HEMISPHHRICA, n.sp. Pl. XXXII. figs. 13, 14. 
The corallum is regularly dome-shaped, and the under surface 
nearly flat, and, as in B. moneta, attached to a shell by a point. 
The common or basal wall is without a trace of epitheca, and the 
corallites, which are distinctly visible from below, have well-formed 
and regular mural coste, which meet at an angle in the shallow 
radiating furrows between the corallites. 
The calices are nearly circular, and very deep. Six principal 
septa project considerably into the calice, their inner margins being 
nearly vertical, and they pass quite to the bottom of the calice, but 
do not pass over the floor of it to the centre, as in Bathycenia 
Slatteri. Six other septa, having much less prominence, pass also 
down the vertical inside of the calice, but diminish in size and 
project so much less that they barely reach the floor. Besides 
these, there are some rudimentary septa, which, however, like the 
others, are subcristiform on the mural region. 
Height of the corallum one inch, and its diameter one inch. 
Diameter of the calices from two to three lines. 
One specimen only appears in the collection. It is from the 
Cornbrash of Le Wast. 
Genus ConvEexastrma, d’Orb. 
ConvExasTR#A Wattoni, Edw. & Haime, Brit. Foss. Cor. p. 109. 
pl. xxii. figs. 5 & 6. 
The exact resemblance which a specimen from the Great Oolite of 
Bléquenéque bears to English specimens from the neighbourhood of 
Burford, Oxfordshire, and Cirencester, Gloucestershire, leaves no 
doubt about the species, and furnishes an entirely new locality 
for it. 
Genus Crrprocenta, d’Orb. 
CRYPTOCENIA OBELIscus, Mich., sp. 
Madrepora obeliscus, Mich. Icon. Zooph. p. 112, pl. 25. fig. 5. 
A specimen from the Great Oolite of Bléquenéque, near Boulogne, 
received with other specimens here mentioned, agrees, both in out- 
* Hist. Nat. Cor. vol. ii. p. 536. 
etd elms 
