28 



TABULATE CORALS. 



sionally regard as a separate group, the MonticuliporidcB) is, 

 again, uncertain. Strong evidence has been brought forward to 

 prove tliat all these forms are Polyzoa ; but it certainly cannot 

 be said that this conjecture has yet been sufficiently established. 

 I shall consider this subject again at greater length ; and I need 

 only add here, that though some of these forms may possibly 

 turn out to be Polyzoa, I am strongly disposed to think that the 

 majority will prove to be true Actinozoa. This seems to be 

 indicated, as a general conclusion, by their close resemblance in 

 many cases to types of an undoubted Coelenterate nature ; by 

 the fact that their coralla are usually or always composed of 

 two sets of corallites, pointing to a heteromorphic condition of 

 their zooids, such as is highly characteristic of many of the 

 Coslenterata, and especially of certain of the Alcyonaria ; and 

 lastly, by the fact that no forms possessing their characteristic 

 features in conjunction have as yet been pointed out as existing 

 among either recent or fossil Polyzoa. 



XII. Labechid.'e. — ^This extraordinary group comprises 

 only the anomalous genus Labechia, E. and H., at present 

 only known as a Silurian fossil. The skeleton in this genus 

 forms a laminar or expanded mass (fig. 12), the under sur- 



Fig. 12.— A, A small specimen of Labechia confer/a, E. and H., from the Upper Silurian of 

 Gotland, of the natural size. B, Portion of the upper surface of the same, enlarged, c, 

 Part of a vertical section of the same, enlarged : a, the calcareous columns, represented 

 as opaque ; b, the lenticular vesicles filled with calcite. 



face of which is covered by an epitheca, while the upper ex- 

 panse shows an apparently imperforate surface, rising above 



