TRIBE I. ASTR^ACEA. 189 



none having the gyri less than a third of an inch broad. The even 

 and more crowded lamellae, simply and regularly denticulate, and the 

 porous bottom of the trenches, distinguish them from the Mussse. 

 They grow to a large size, but none, as far as is known, reach the 

 gigantic dimensions of some Astrseas. 



Worn specimens of this genus are recognised by their stipitate form, 

 evenly though faintly striate exterior, porous or semisolid line along 

 the centre of the trench, and the regular lamellae usually seven or 

 eight to a quarter of an inch though sometimes ten or eleven, espe- 

 cially at the margin of the trench. 



The MariiciiiEe are confined to the coral-reef seas, and are most 

 abundant in the West Indies. 



This genus was instituted by Ehrenberg, for certain of Lamarck's 

 Meandrinse, characterized by growing from a pedicel or central at- 

 tachment. Ehrenberg also included, though with an expression of 

 doubt, some of the massive meandrine Mussa?, besides the groups 

 Ctenophyllia and Tridacophyllia. 



Arrangement of the Species. 



I. Calicles separated by open intervals. (Segregate species.) 

 *1. M. amarantum. 



II. Calicles coalescing laterally, and forming for the most part a single ridge, usu- 

 ally sulcate, between adjacent fossce. (Aggregate species.) 



2. M. fissa. *5. M. hispida. 



*3. M. areolata. *6. M. prserupta. 



*4. M. meandrites. *7. M. dilatata. 



1. MANICINA AMARANTUM. (Dana.) 



M. segregato-gemmata, grandis, convexa ; discis sinuosis. Corallum cali- 

 culis meandrinis ; fossis \-\\" profundis, scepius perpendicularibus et 

 J" latis, sed margine 1" dilatatis, fundo angustissimis et non porosis ; 

 collibus,fere 2'" crassis. 



Segregato-gemmate, large, convex ; disks sinuous. Corallum having 

 the calicles meandrine ; fossa 1 to 1 J inches deep, usually perpen- 

 dicular and \ of an inch broad, but often dilating to 1 inch towards 

 the margin, at bottom very narrow and not porous; ridges rounded, 

 near 2 lines thick. 



48 



