CORALS FROM THE GREAT OOLITE. 109 
Genus CONVEXASTREA.' 
ConvexastrEA Watton. ‘Tab, XXIII, figs. 5, 5a, and 6. 
Corallum composite, massive, convex, more or less gibbose, or even dendroid. — Calices 
small, rather unequal, and more or less closely set. The parts that have been worn down 
show that the walls are circular and the visceral chambers very narrow; but in the parts 
that remain entire the edge of this investment is completely hidden by the septo-costal 
lamella which are exsert and somewhat cristiform. These radii are twelve in number, and 
constitute, therefore, two complete cycla; they are very thick, of unequal length alternately, 
and in general separated from those of the surrounding corallites by narrow subpolygonal 
furrows, but sometimes one or two of them join these, and others establish an imperfect 
confluence between the adjoming individuals. The septa become rather thin inwards, and 
present small spiniform granulations on their lateral surfaces. There appears to be no 
columella. Diameter of the corallites almost a line; diameter of the mural investment 
half a line. 
This species was found in the Great Oolite at Hampton Cliffs, near Bath, by Mr. 
Walton, in whose collection are placed the specimens here described. The fossil which 
Mr. M‘Coy refers to the Astrea reticulata of Goldfuss, and was found at Minchinhampton, 
may probably belong to this species. By its general aspect C. Waltoni bears some resen- 
blance to the Gosau fossil figured by Goldfuss, but the latter belongs to the genus 
Astrocenia, and differs fromthe above-described species by its polygonal walls, its non- 
exsert septa, and its styliform columella. 
The genus Convexrastrea has been recently established by M. D’Orbigny, for a species 
found at St. Cassian, and very well figured by M. Klipstein under the name of Astrea 
regularis.” This new division is very nearly allied to Stylina (p. xxix), and may be defined 
by the following characters : 
Corallum massive, astreiform, increasing by extracalicular gemmation ; calices circular, 
and separated from each other by circumvallating furrows, through which the costal lamin: 
do not pass (excepting sometimes low down in the corallum); no columella; septa not 
numerous, and slightly exsert. 
described in our Monograph of the Astreide, under the name of Stylina astroides, and which must vow be 
called Stylina alveolata. (See our ‘ Memoir on the Paleeoz. Corals,’ &e., p.59.) It is also to be noted, that 
the same species has been referred by Blainyille to an unrecognisable fossil mentioned by Schlotheim, and 
has been named by that zoologist, Siderastrea cavernosa. (Dict. des Se. Nat., vol. Ix., p. 336, and Manuel 
d’Actinologie, p. 371.) 
1 D’Orbigny, note, ‘Sur des Polypiers Fossiles,’ p. 9, 1849. 
2 Beitr., etc. tab. 20, fig. 11. 
