GENERAL FORM. 27 



the specimens sent to me by Bargatzky) to be Stromatopora Beuthii, Barg. I 

 should also be disposed to think that the form named Gaunopora placenta, Phill., 

 is really identical with S. Beuthii, Barg., but the fragment sent me by Dr. Maurer 

 is much crystallised and altered, and I should not like to be positive on this point. 

 Stromatopora maculosa, Maur., is seemingly a true Stromatopora, and is related to 

 S. Beuthii, Barg., or to S. Hiipschii, Barg., standing apparently very near to the 

 latter; but in this case also the state of preservation is very bad. S. hainensis, 

 Maur., I have not seen, and I am not able, therefore, to give any personal opinion 

 as to its relationships ; but it may perhaps be compared with the form which I 

 have named Stromatoporella eifeliensis. Lastly, it may be mentioned that Dr. 

 Maurer excludes from Gaunopora all those examples in which there exist imbedded 

 tubes with definite walls, and having horizontal connecting-tubes. Of all such 

 examples he takes Roemer's view, namely that they are the result of the com- 

 mensalism of a Coral with a Stromatoporoid. He therefore understands by 

 Gaunopora something quite different to what has been usually understood by this 

 name. 



II. GENERAL STRUCTURE OF THE SKELETON OP THE 



STROMATOPOROIDS. 



1. General Poem and Mode op Growth. 



As regards their general form, the Stromatoporoids present themselves under 

 the most varied aspects, while the mode of growth, though less variable, is also 

 not absolutely constant even among the individuals of a single species. As a 

 general rule, however, each species has a more or less highly characteristic form 

 and mode of growth, from which it only departs when subjected to changes in its 

 conditions of existence. The typical form of the skeleton of the Stromatoporoids 

 is that of a hemispherical mass or a flattened expansion, attached by a narrow 

 peduncle, or directly, to some foreign body, but having the under surface covered 

 by a concentrically wrinkled imperforate epitheca, while the apertures for the 

 emission of the polypites are carried upon the upper surface. In form and mode 

 of growth, therefore, the majority of the Stromatoporoids may be, with complete 

 accuracy, compared with the massive or laminated species of Favosites, Pachypora, 

 Alveolites, or Michelinia. In a large number of species (such as Labechia conferta, 

 E. and H., Stromatoporella granulata, Nich., Clathrodictyon striatellum, D'Orb., 

 G. fastigiatum, Nich., Stromatopora discoidea, Lonsd., &c), the form of the 



