96 BRITISH FOSSIL CORALS. 
closely set. The above-described species bears the closest resemblance to L. helianthoides,' 
I. Bernardana, I. ornata,’ and I. Greenoughi,* and it is often difficult to distinguish 
them. In &. helianthoides the calices are in general more regular, and the sepfa are less 
numerous, and not so strongly granulated; in LZ. Bernardana and I. ornata the septa 
are more distant and less granulated on their lateral surfaces ; and in J. Greenoughi the 
calices are larger, the septa thinner, and the marginal dentations of these less developed. 
As to the new species which M. D’Orbigny has lately mentioned as appertaining to the 
Oolitic formation,’ they are mostly established on specimens that are in avery bad state of 
preservation, and do not seem to us susceptible of being satisfactorily characterised.° 
2. Isastrea Greenoveni. ‘Tab. XVIII, fig. 2. 
It is not without much hesitation that we have separated specifically this fossil from 
I. eaxplanata, for we have seen but a small fragment of it in the collection of the Geological 
Society. It is in fact very similar to the preceding species, but differs from it by the calices 
being all larger, and the septa being on the contrary thinner in proportion and less denti- 
culated. The corallum appears to have been almost flat at its upper surface, and gemmates 
at a considerable distance from the fossulee. The calices are shallow, and the edge is obtuse ; 
the fossula is circular, well defined, and appears to be closed by dissepiments without con- 
taining any columellarian trabicule. The seyfa form four complete cycla and an incomplete 
fifth cyclum ; there are often as many as fifty-six; they are thin, broad, slightly flexuous, 
but little prominent, and not very closely set. Those of the second cyclum are as large as 
the primary ones, and reach to the central fossula; the tertiary ones are also large, but 
those of the fourth cyclum are much smaller. They all appear to be very delicately denti- 
culated at their upper edge, and slightly striated laterally. The dissepiments seem to be 
highly developed. ‘The great diagonal of the calices varies from six to seven lines. 
This fossil was found at Botley Hill by Mr. G. B. Greenough. 
l Astrea helianthoides, Goldfuss, Petref., pl. xxii, fig. 4a. (Cet. excl.) 
2 Prionastrea Bernardina, D’Orbigny, Prodr., vol. i, p. 293. 
3 Prionastrea ornata, D’Orbigny, Prodr., vol. i, p. 293. 4 Tab. xviii, fig. 2. 
> Prod. de Paléont., vols. i, ii. 
® We must also beg leave to remark that the Astrea dissimilis, (Michelin, Icon., tab. xciv, fig. 12,) 
for which M. D’Orbigny has made the new general division Dendrastrea, (Prod., vy. i, p. 322,) differs only 
from Isastrea by its general form, and that the same species is again entered in that palzontologist’s 
Catalogue under the name of Dendrastrea Langrunensis, D’Orb. (Prod., v. i, p. 322.) 
