INTRODUCTION. XX1X 
23. Genus PLEROGYRA. 
Milne Edw. and J. Haime, loc. cit., p. 284, 1848. 
Corallum composed of long, thick, slightly ramified gyri, united laterally by their lower 
part, and free only near the calicular margin. No columella. Septa exsert, and broad ; 
interseptal loculi very broad, and almost entirely filled up with large vesicular dissepiments, 
constituting a cellular mass. Malls presenting some costal striee near the calicular margin, 
but covered in all the other parts by a vesicular structure, which becomes highly developed 
between the gyri. 
Typ. sp., Plerogyra laxa, Milne Edw. and J. Haime, loc. cit., tab. vi, fig. 8 
Section IT1].—EUSMILINA) AGGREGATA. 
Corallum composite and massive, in which the corallites are not arranged in series, 
and although remaining quite distinct, are united together by their walls, by a costal 
ccenenchyma, or by mural annular expansions. 
This group corresponds to the division of the Astreine aggregate of the second tribe of 
this family, and constitutes with these the great genus Astrea of most authors. 
24. Genus STYLINA. 
Lamarck, Hist. des Anim. sans Vert., t. 1, p. 220, 1816; Fuscieularia, Lamarck, Extrait du Cours, 1812. 
Corallum glomerate, astreiform. Cora/lites very tall, united by means of the costal 
system and its dissepiments, and having the appearance of small truncate cones at their 
upper end. Cadices circular, with their margin free; usually distant from each other. 
Columella styliform and projecting. Sepfa exsert, arched at their apex; in general not 
numerous, and forming as usual six systems. No pali, Walls thick. 
Typ. sp., Stylina echinulata, Lamarck, loc. cit.; Milne Edw., Atlas du Regne Animal de Cuvier, 
Zooph., pl. lxxxv, fig. 3 
25. Genus STYLOC@NIA. 
Milne Edw. and J. Haime, An. des Sc. Nat., 3™° série, t. x, p. 298, 1848. 
Corallum having the form of a very thick sheet, convex or bent in different ways ; 
covered inferiorly by a finely-striated epitheca; and mereasmg by marginal gemmation. 
Corallites united by their walls, which are thin and prismatic. Calices polygonal, their 
margins simple, and bearing at their angles small, columnar, grooved processes. Colwmella 
styliform, projecting. Septa very thin, not exsert, nor numerous, and forming six systems. 
Typ. sp., Stylocenia emarciata, Milne Edw. and J. Haime, loe. cit., tab. vii, fig. 2; Astrea emarciata, 
Lamarck, op. cit., t. u, p. 266. 
