24 PALAEONTOLOGY 



The Devonian system contains about 150 described corals, 

 the carboniferous limestone 7G, and the magnesian limestone 

 only 5 or (J. The commonest forms of simple, turbinated 

 corals, are Cyathopliyllum (tig. 4, 2 and 3), which exhibits four 

 slight fossulce in its cup, and is often supported by root-like 

 processes. In Zaphrentis (fig. 4, 5) there is but one deep 

 fossula. Amplexus (tig. 4, 1) is a characteristic carboniferous 

 fossil, nearly cylindrical, and often so straight and regular in 

 its growth as to have been originally described as a chambered 

 shell. The radiating septa are very slight, and the horizontal 

 partitions simple, fiat, and almost as regular as the septa of 

 the Orthoceras. In the Silurian Cystipihylhim (fig. 4, 4) the 

 lamellse are also evanescent ; but the tabulce are represented 

 by numerous vesicular plates. The corals of these genera are 

 not always solitary, or merely in groups ; some species of 

 Cyathopliyllum constantly form compound masses, with cups 

 rendered polygonal by contact, like C. regiv/m of the Bristol 

 limestone. The allied genus Acervularia (fig. 4, 8) resembles 

 an Astrart, and exhibits, in a remarkable manner, the multi- 

 plication of its corallites by calicular gemination. The genus 

 Litkostrotion (fig. 4, 7) of the carboniferous limestone is also 

 compact and asteeiform, but the new corallites are produced 

 by lateral gemmation. Corals, with the same structure, but 

 not compact, are known by the name Lithodendron (fig. 4, 6). 

 The " chain-coral" Halysitcs (fig. 4, n) and Syringopora (fig. 

 4, 10) resemble, at first sight, the recent asteroid Tiibiporidcc : 

 in Halysitcs the radiating septa are quite rudimentaiy ; and 

 in Syringopora the tabulse are funnel-shaped, forming a central 

 axis to each tube. The Favositidcc. (fig. 4, 12) are mostly very 

 regular both as to their polygonal shape and transverse tabulse ; 

 the culls of adjacent corallites are connected by pores, either 

 in the sides or angles of the Avails ; the septa are rudimentary. 

 In the genus Clicclctes the tubes are always slender, and much 

 elongated, and their walls imperforate. Miclidinia resembles 



