566 Reviews — Nicholson's Tabulate Corals. 



walls of the tubes bounding the calicles, and therefore cannot be 

 compared with the regular normal septa which are met with in 

 Heliolites, and which in some instances extend nearly to the centre 

 of the corallite. The pseudo-nature of the septa of Heliopora 

 sufficiently explains the absence of all correspondence between their 

 variable numbers and the number of the mesenteries; but it is 

 highly probable that the septa of Heliolites indicate a similar 

 number of mesenteries in the living animal ; and as there are pretty 

 constantly twelve septa, it follows that the animal could not have 

 been Alcyonarian. There is no doubt that Heliolites and some of 

 its allied forms possessed two kinds of zooids, the same as Heliopora; 

 but a corallum of larger and smaller tubes indicating this, is also 

 found in the Monticuliporidaa, Halysitidee, and not improbably in 

 some of the Favositidae, whilst it is very doubtful whether the genus 

 Lijellia, Edw. and EL, here placed with Heliopora and Heliolites, 

 actually possessed smaller incomplete zooids ; for the intermediate 

 structure between the larger corallites, instead of being tubular, is 

 distinctly vesicular — the larger corallites themselves closely re- 

 semble those of a typical Heliolites. We therefore think that the 

 evidence is insufficient to conclude that Heliolites and the allied 

 Palaeozoic genera above named are truly Alcyonarian the same as 

 Heliopora. 



Two chapters, the twelfth and thirteenth, are devoted to a con- 

 sideration of the families of the Chastetidas and Monticuliporidae, and 

 the author believes that he has discovered satisfactory grounds of 

 division between these very confusing groups. To the Chastetidas 

 are referred corals with uniform corallites, having the walls com- 

 pletely amalgamated, and but few and remote tabulae, whilst the 

 Monti culiporidae are distinguished by corallites of different sizes in- 

 dicating the existence of two kinds of zooicls ; their walls are not 

 fused with each other, and the tabulae are well developed. The 

 author rejects the idea which has been proposed to place these 

 families with the Polyzoa, though it is very probable that many of 

 the incrusting forms probably belong to this higher group of animals, 

 and is disposed to regard them as a special group of Alcyonaria. 



In the final chapter the family Labechidae is treated, and the 

 characters of the very aberrant genus Labecliia are described. The 

 absence of all apertures on the surface of the corallum of this form 

 and the peculiar projecting solid calcareous rods render it so different 

 from all other groups of corals, that its relations must for the present 

 remain a matter of conjecture. 



In concluding our notice of this work we desire to express our 

 admiration, not only at the unwearied industry of the author in 

 bringing together such an amount of research into the characters 

 and relations of these ancient corals, but also at the very excellent 

 manner in which the treatise is published. In addition to the wood- 

 cuts in the text, there are fifteen beautifully executed lithographed 

 plates, mostly illustrating microscopic sections, and the drawings 

 for these have been made by Dr. Nicholson himself. Whatever 

 future discoveries may disclose as to the affinities of these corals, 



