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Summary. — The general facies of these interesting corals is that of 

 the Australian tertiary beds, as far as we are acquainted with them. 

 None of the species are however known. Some of the genera have 

 been found in other beds. These are — Deitocyathus, Trochocyathus, 

 Amphihelia, and, doubtfully, Conosmilia. Our Deitocyathus, as already 

 observed, is closely allied to, if not identical with, D. italicus. That 

 species is common in the Cape Otway beds in Victoria, and is living in 

 the West Indian Seas. It will require a careful comparison to deter- 

 mine if our fossil is the same. It is very abundant apparently at 

 Aldinga. We have two species of Trochocyathus already described. 

 Both are very distinct from the Aldinga species, -which is much 

 smaller, and has a well-marked basilar scar. We have one of the 

 species living in the Port Jackson. Professor Duncan thinks that the 

 genus can hardly be separated from Deitocyathus ; but if my remarks on 

 the absence of a true columella are found to hold good for all the 

 species, the distinction is a justifiable one. D. Tateanus comes near to an 

 existing form. The flattened character may, however, vary, as we see 

 that in the case of D. Aldingensis these are features which vary much 

 at different ages and for different individuals. In Amphihelia striata 

 and A. ziczac we have two forms of Oculinidw, which are of great inte- 

 rest. They are both closely related to our existing Australian A . venusta, 

 but are very different from our tertiary fossil form, A. incrustans, which 

 I venture to suggest would perhaps have been better placed in a genus 

 by itself. Both the Aldinga fossils in their structure throw a re- 

 markable light upon the mode of growth of these corals. We see not 

 only that the calices fill up from below in some instances, but not at all 

 in others, a circumstance clearly dependent upon the exigencies of the 

 animal, or perhaps upon its size. This gives us a glimpse of the very 

 artificial manner in which our great divisions of the Madreporaria are 

 classified, and makes us fear that as the habits and economy of the 

 animals and their stony dwellings are studied the whole arrangement 

 will have to be remodelled. Amphihelia did not, as far as we know, 

 make its appearance until the tertiary period. The Oculinidoz generally 

 are entirely a recent family, extending to the Mesozoic rocks, but only 

 four genera are found in them, and only two below the chalk. The only 

 fossil species of Amphihelia known are those from Australia. 



I have already observed the position that the new genera of Troeho- 

 smiliacece take in the classification. They are a series of simple corals 

 with scanty endotheca, in which respect they are related to Upper Meso- 



