the development of their costae. They have not a close affinity with the recent Trochocyathi of New Zealand ; and the subhemispherical form somewhat resembles the Miocene species of Tortona and India. One of the species is probably the " Petraia " mentioned by Mr. Wilkinson. The only living Trochocyathi are found off New Zealand. The genus culminated in the Miocene of Europe; and species of it were rare in the West-Indian deposits.
Deltocyathus italicus is a well-marked form, although the genus is hardly worthy to be separated from Trochocyathus. The shape and ornamentation of the corals are most beautiful ; and they form the prettiest of all the miocene Madreporaria of Europe. Very lately Count Pourtales dredged up many specimens of dead Deltocyathi in 270 fathoms off Havanna, one of which he sent to me. A careful examination of the Miocene, West- Indian, and Australian forms leads to the belief that they are not specifically distinct, and that no one would consider them other than varieties if the localities whence they had been derived were unknown. There is a slight difference in shape, but nothing at all specific ; and the costae are more moniliform in one and more spiny in another specimen. As I cannot distinguish a specific difference, I have called the Australian form " variety australiensis;" and I would suggest that Pourtales's Deltocyathus Agassizi should be known as variety Agassizi of the species italicus. The Deltocyathi are small forms and very readily passed over ; but I could not find any amongst the collections of fossil West-Indian corals I have examined. No species have been found in the great Coral ocean.
The Sphenotrochi of the Australian Cainozoic deposits differ from all others in having a curious notch at the base. In one species this is so marked as to produce the appearance of two lateral processes on either side of the base. They present, moreover, an anomalous relation between the septa and the costae. The existing species of the genus are found around the S.W. of England and the Irish coast ; and the fossil forms are to be distinguished in European Eocene and Miocene strata and in the Crag. All these have the septa continuous with the costal projections. The Australian species have the septa not continuous with the costae, but with the intercostal spaces, so that the costae are on the outside of the interseptal spaces. No living species of the genus have been found in the great Coral ocean, or in the West Indies. The alliance between the genera Sphenotrochus and Placotrochus is strengthened by the discovery of the Australian forms of the former genus.
Conotrochus is a genus founded upon some well-marked Sicilian corals by Seguenza. They were found in the uppermost of the so-called Miocene strata or the " Marne Giallastre," which are below the horizon of Flabellum siciliense, Edw. & H. (lowest beds of Older Pliocene). The generic characteristics are those of a Turbinolian without pali. The corallum is simple, fixed when young, free when old. The columella is fascicular and well-developed. There is a strong epitheca. The shape of the corallum is clavate, turbinate, cylindro-conical, straight or curved.
