Mr. H. J. Carter on the Stromatoporidffi. 313 



lierself, in general forms especially, and therefore that like 

 forms are not always accompanied by like functions. 



What the surface of Caunopora was like in its original state 

 I do not know, as all the specimens that I have seen are too 

 weathered to describe this satisfactorily. Perhaps it was like 

 that of Parheria^ whose structure elementarily very much 

 resembles that of Caunopora ; that is, the surface con- 

 sisted of gentle elevations more or less irregular in their form 

 and diameter. But internally the tubes are often united by 

 cross branches, similar to Syringopora in this respect, although 

 widely different otherwise, as the tubes of Caunopora are 

 united by the curvilinear coenenchyma, while Syringopora, like 

 Tubipora musica, had notliing between its tubes. Again, a 

 branch of the " stelliforra " groups of vessels is often con- 

 nected with one of these calicular tubes, showing that the 

 calicle and vessels may be combined, and developed from each 

 other, as the case may be. 



All this has been witnessed in the Milleporidee by Mr. 

 Moseley, who states {p'p. et loc. cit.) that " the thin incrusting 

 films of Millepora, when dead and dry, show well the ramifi- 

 cations of the canal-systems and their connexion with the 

 calicles " (p. 120), and " in some cases large tertiary branches 

 of the canals join the zooid-cavities directly" (p. 125). 



Thus in all essential points the structure of Caunopora pla- 

 centa was the same as that of Millepora alcicornis ; only the 

 large-branclied vascularity of the " proliferous membrane,'" or 

 hydrophyton, instead of straggling over the surface, was deve- 

 loped from more foci, and thus brought into more stelliforra 

 shapes. Even in tlie Strom atoporidfe this differs in degree, 

 as may be seen by comparing Baron Rosen's lithograph of his 

 Stromatopora elegans (Taf. iii. fig. 1) with that of 8. Hclimidtii 

 (Taf. iv. fig. 1, op. cit.), which, as before stated, was probably a 

 Caunopora) ; while in the specimen of Stroniatop>ora mammil- 

 lata, Nich., from which fig. 10, pi. 1 (Linn. Soc. Journ. I. c.) 

 was taken, which came from Canada West, and was shown 

 me by Dr. Murie, both the straggling and stellate forms of the 

 vascularity are present on the same surface. 



We now come to S. concentrica, Goldf, ; but who has de- 

 fined this species ? Certainly not Goldfuss, either in his dia- 

 gnosis or in his illustration. Thus, when authors speak of S. 

 concentrica, I, after having now studied the Silurian and De- 

 vonian species probably as extensively as any one living, 

 whereby a repetition of the same forms in every collection, 

 both English and American, has been witnessed, am thus in- 

 clined to think that I have seen specimens of the greater part 

 of the species ; yet I am at a loss how to define S. concentrica, 



