TRIBE I. ASTRjEACEA. 173 



surface is striated, and when fresh is alive for an inch and a half from 

 the margin : the lamellae also are much thinner, and the septum hardly 

 exceeds one-twentieth of an inch in thickness. 



GENUS III. MUSSA. OKEN. 



Astrtzida, maxima, gemmatione segregate et interdum explanato-glo- 

 meratce. Tentacula numerosa, incequalia, internis tumidis. Corolla 

 caliculato-ramosa, aut explanato-glomerata ; caliculis crassimis, sub- 

 turbinatis aut latissime compressis ; cellis suborbiculatis aut elongate 

 meandrinis, extus crasse lamello-striatis et echinato-dentatis ; lamellis 

 dentatis vel indso-dentatis, incequaliter exsertis. 



Large Astraeidae, segregate, also explanato-glomerate ; tentacles nume- 

 rous, unequal, the inner tumid. Coralla calicularly branched or 

 explanato-glomerate ; calicles very stout, subturbinate, with orbi- 

 culate or lobed cells, sometimes very broadly compressed with the 

 cells long meandering ; exterior stoutly lamello-striate and echinato- 

 dentate ; lamellae coarsely dentate or gash-toothed, unequally exsert. 



This genus includes the largest coral animals of the Astrsea family. 

 Two inches in diameter is no unusual size, and when fully expanded 

 they look like large Actinia?. The broad-tinted disks fringed with 

 crowded rows of tentacles, the inner differing generally in form and 

 colour from the outer, make the most beautiful exhibition of living 

 flowers in the coral seas, especially when a whole corymb or hemi- 

 spherical group is in full expansion. 



The coralla often form regular hemispheres, consisting of calicular 

 branches. The calicles have large concave cells, arid stout gashed 

 lamella? very unequal and unequally exsert, with the exterior ribbed 

 with extensions of the same dentate lamellae. There are only six or 

 eight lamellae in a breadth of a fourth of an inch, and half of these are 

 usually obsolescent. In size, the Mussae thus far known vary from 

 three-quarters of an inch to three and a half inches in diameter. In 

 a few species the cells are very long meandering, and belong to a 

 large number of united polyps. The tentacles in these species margin 



44 



