28 



TABULATE CORALS. 



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

 again, uncertain. Strong evidence has been brought forward to 

 prove that 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 Ccelenterate 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 

 Caslenterata, 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^:. 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 conferta, 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 



