18 
TRIBE I. ASTR.EACEA. 
and angular ; lamellse strongly dentate ; margin of calicle not revolute, sub- 
acute. 
Red Sea. Foj'skal, Ehrenherg. 
5. Mussa cactus {Dana). — Regularly hemispherical; disk usually sub- 
orbiculate, green; inner tentacles bursiform, pearl white and brown at tip, 
outer a little elongate and brown. Corallurn having the branches crowded, 
calicles sometimes 2 to 3-lobed, 1 to 11 inches thick, subturbinate, exterior 
irregularly lamello-striate and serrate; lamellas unequal, strongly dentate, 
rounded at apex, with 3 to 5 subtriangular teeth. 
Plate 7, fig. 1, hemispherical clump natural size, with part of the polyps ex- 
panded ; 1 a, tentacle enlarged ; 1 &, vertical section of a calicle ; 1 c, trans- 
verse section. — Feejee Islands. — Exp. Eip. 
6. Mussa costata [Dana). — Hemispherical; disks usually suborbiculate. 
Corallurn having the branches crowded ; calicles f to 11 inches broad, scarcely 
turbinate, elongate, exterior ribbed angular, with rarely a tooth ; lamellse very 
unequal, dentate, the larger broad, truncate at apex, and often 2-3-gash- 
toothed. 
Plate 7, fig. 2, a calicle natural size ; 2 a, 2 6, lamellse. — Tahiti, Society 
Islands, — E.ip. Exp. 
II. Caliculato-ramose ; cells often elongate and sinuous. 
7. Mussa sinuosa [Lamarck). — Hemispherical ; disks usually elongate and 
meandering. Corallurn with the branches f to H inches thick, usually much 
compressed, exterior striate and for an inch or more seri-ato-dentate ; cells 
sometimes simple, but often sinuous and 2 to 5 inches long; lamellse stout, 
broad dentate and inciso-dentate, ^ to d an inch exsert ; intervals between the 
calicles, nearly half an inch broad. 
Plate 8, fig. la, 1 6, 1 c, outline of cell and lamellse. — East Indies, Esper^ 
Gnielin. — Red Sea, Ehrenherg. 
8. Mussa cytherea [Dana). — Regularly hemispherical ; disks mostly linear 
and meandering. Corallurn having the branches usually much compressed, 
^ an inch thick, and f to 5 inches broad, closely crowded ; exterior striate 
above, and sparingly echinate ; cell often 5 inches long and sinuous ; larger 
lamellse much exsert with 3 to 5 smaller intermediate, subtruncate at apex 
and 2-3-gash-toothed. 
Plate 7, fig. 3 a, 3 6, 3 c, section of cells showing the outline of the lamellse. 
— Tahiti, Society Islands. — Exp. Exp. 
9. Mussa multilobata [Dana). — Animal chestnut-brown; disks long, sinu- 
ous, and multilobate, bright green. Corallurn meandrine, calicles f of an inch 
wide, cell very much gyrose, at bottom 3 or 4 longitudinal lamellse ; lamellse 
