distinguished from Millepora. 29 



deavoured to eliminate the misleading appearances due to 

 peculiar states of preservation, association with foreign organ- 

 isms, &c., and had arrived at the conclusion, stated in a 

 memoir now in the hands of the Secretary of the Geological 

 Society, that these fossils appertain to the group of Rhizopods. 

 In these circumstances my attention was naturally attracted 

 by the association of things known to me as very distinct in 

 the heading of Mr. Carter's paper, " Identity in Structure 

 of Milleijora cdcicornis and Stromatojjora.'''' After reading the 

 paper I betook myself to the reexamination of the specimens of 

 Millepora in our collections, but, I must confess, with the 

 result of failing to find any indications whatever of the affini- 

 ties so confidently asserted by Mr. Carter. 



The typical Stromcdoporce, as Hall, Nicholson, and Win- 

 cliell have shown, and as any one can see for himself in the 

 well-preserved specimens from our Corniferous Limestone, 

 are composed of thin concentric laminas, perforated with 

 minute pores, and connected with hollow and solid pillars. 

 The allied forms known as Caunopora and Goenostroma have 

 in addition a secondary deposit between the laminae, through 

 which pass branching horizontal tubes or canals radiating from 

 vertical tubes or bundles of tubes traversing the laminae, and 

 corresponding to the hollow pillars of the ordinary Stromato- 

 porce. These structures are detailed and figured in the paper 

 already referred to. 



The corallum of Mille])ora, on the contrary, has no con- 

 centric laminee, though it sometimes presents accidental layers 

 occasioned by interruptions of growth. Its structure is can- 

 cellate or reticulate, consisting of minute calcareous rods, 

 completely confluent, and leaving irregular and vermicular 

 interstices, only occasionally presenting the appearance of 

 horizontal canals. It is penetrated with cells of two sizes, 

 which are divided into compartments by distinct tabulee. The 

 structure is that of a tabulate coral with its cells imbedded in 

 a copious reticulate coenenchyma. 



Though Mr. Carter appears to maintain that the horizontal 

 passages sometimes seen in Millepora are homologous with 

 the canal-system of Stromatoporid^, in one place he says, 

 " We have every thing structural in the corallum of Millepora 

 alcicornis that is to be found in Stromatopora, excepting the 

 stelliform systems of venation." Perhaps this apparent incon- 

 sistency arises from his not being aware of the fact that the 

 stelliform or radiating canals do not occur in the common 

 species of Stromatopora^ but only in Goenostroma and Gauno- 

 pora, and that in these they are not superficial, except in 

 broken or eroded specimens, but belong to the secondary or 



