Ixxvili BRITISH FOSSIL CORALS. 
12. Genus XEnta. 
Savigny, Egypte, Atlas and op., Lamarck, op. cit., vol. il, p. 629, 1816. 
Polypi forming subramified masses, as in Aleyonium, but not retractile, and not having 
a thick coating of spicule at the basis of the tentacula. 
Typ. sp. Xenia umbellata, Savigny, Egypte, Polyp., tab. i, fig. 3. 
13. Genus NEPHTHYA. 
Savigny, Atlas de Egypte; Blainville, Manuel d’Actinol, p. 523; Spoggodes, Lesson, Illustr. de 
Zoologie, 1831. 
Polypi forming arborescent masses, incompletely retractile, and having the borders of 
the calice thick and incrustated with large navicular spicule. 
Typ. sp,, Nephthya Chabroli, Audouin, ap. Savigny, Egypte, Pol. tab. ii. fig. 5. 
14. Genus PARALCYONIUM. 
Alcyonidia, Milne Edwards, Ann. des Sc. Nat. 2d series, vol. iv, p. 323. 
Polypi resembling Nephthya, but bemg completely retractile, and having the lower 
part of the common mass incrustated with a thick coating of long navicular spicule, but 
the upper part membranaceous and retractile. 
Typ. sp., Paraleyonium elegans ; Alcyonidia elegans, Milne Edwards, loc. cit., tab. xii and xiil. 
15. Genus SARCoPHYTON. 
Lesson, Zoologie du Voyage de la Coquille, Zooph., p. 92, 1831. 
Differs from the genus Aleyonium by the great abundance and the peculiar structure 
of the common tissue, the cells of which are tubular, and arranged with great regularity 
in fasciculi, perpendicularly to the upper surface of the mass. 
Typ. sp., Sarcophyton plicatum, Valenciennes MSS.; Sarcophyton lobulatum, Lesson, loc. cit. ; Aleyo- 
nium plicatum, Lamarck, Hist. des An. sans Verteb., vol. ii, p. 395. 
16. Genus CESPITULARIA. 
Valenciennes MSS. 
Polypi non-retractile, arranged in fasciculi, and united in the greatest part of their 
length by a dense, tough, common tissue, as in Alcyonium. 
Typ. sp., Cespitularia multipinnata, Valen.; Cornularia multipinnata, Quoy and Gaimard, Voyage de 
l’Astrolabe, Zooph., tab. xxii, figs. 1-4. 
