328 TURBINOLIAD.E. 



Milne Edwards, indeed, considers the Sphenotrocht with 

 papillate and crisped ribs to be in no case later than the 

 eocene deposits ; while those with smooth ribs he looks 

 upon as invariably belonging to higher strata, and reaching 

 to the present period : but this is a canon which a new 

 species may at any moment overturn, if it be not already 

 subverted by the 8. nanus (Lea) of the eocene of Alabama. 

 Dr. E. P. Wright mentions, as a suspicious circumstance, 

 that many pleistocene shells do exist in the bed of shelly 

 sand, where these specimens were found. But this does not 

 confirm Professor Milne Edwards's rule ; for, so far as 

 that could decide the question, it would prove not only 

 that this crisped Coral is not recent, but that it is certainly 

 as old as the miocene. 



Dr. Wright says : — " I have reason to think, however, 

 that they are not fossil ;" and the same is my own impres- 

 sion, though I can scarcely assign any definite grounds for 

 it, except the fresh appearance of one or two of the speci- 

 mens. Some of them are rubbed, and one is polished 

 externally. 



The uniformity in size of the individuals, and the full 

 development of the plates, indicate a probability that, 

 minute as they are, they have attained adult age. 



[mixtus (foss.).] 



[crispus (foss.).] 



Weightii. 



[Ceratotrochus (foss.).] 



