710 R. F. TOMES ON THE OOLITIC 
idea of the age of the specimens is desirable before placing too much 
reliance on this as a specific character. 
MonTLivALTIA CARYOPHYLLATA, Lamx. 
A considerable number of specimens of Montlivaltie are now be- 
fore me, all of which, though differing considerably in their com- 
parative height and diameter, are constant in having exsert septa, 
uniformity in the number of the cycles in all the larger examples, 
and in elongated fossula. They are specifically undistinguishable 
from English specimens from Fairford, and from Milton in 
Oxfordshire. The collection contains oe: from Marquise, 
Hydrequent, and Le Wast. 
Montrivart1a Rieavxi, n. sp. Pl. XXXII. figs. 15-17. 
The corallum has a more or less depressed form, as in Monilwvaltia 
lens. It is ovoid, and the upper surface has a swollen or inflated 
appearance. The wall is horizontal, and does not extend to more 
than three fourths of the diameter of the corallum; but unlike that 
of M. lens, it is slightly convex, and is almost wholly without con- 
centric wrinkles. The fossula is deep and considerably elongated in 
the direction of the greater diameter of the corallum, of the entire 
length of which it occupies about one third. The septa project be- 
yond the basal wall considerably, and their upper margin is much 
arched. ‘They are nearly straight, but curve a little at the fogsula, 
and are thin, and have their sides ornamented with very thin ver- 
tical ridges, which are rather far apart, and terminated at their 
margins in very small and rather distant points. The intervals 
between these ridges are of twice the breadth of the ridges themselves. 
The cycles are rather difficult to trace, owing to the irregular de- 
velopment of the later ones; but there are about 120 visible septa. 
Of these the primary and secondary pass quite into the fossula. 
The tertiary ones are fully three fourths of the length of the pri- 
mary ones, and those of the fourth cycle are about half the length 
of the primary ones. 
Greater diameter of the corallum 1 inch 5 lines, shorter diameter 
1 inch 2 lines. Height 8 lines. 
From the Monilivaltia lens the present species differs very mate- 
rially in its greater size, more inflated or bulging form, and longer 
fossula, and by its thinner septa and their thinner and more distant 
ridges, ending in smaller and more separated denticulations. Added 
to these differences is the comparatively small extent of the basal 
wall, which is never concave, as in MM. lens. MM. Milne-Edwards 
and Haime have referred a species of flat Montlvaltia from Mar- 
quise, which is no doubt the present one, to their lV. depressa* ; 
but specimens of the latter obtained from the type-locality by the 
late Mr. Walton, and obligingly given to me, differ very materially 
from. the French specimens received from M. Rigaux. Of the speci- 
mens of M. depressa collected by Mr. Walton I shall have occasion 
* Hist. Nat. Corall. vol. ii. p. 326. 
