48 MYCKDIUM. 



Diinonsions slightly smaller than tliose ol" Dlascris pumlla. Both 

 species are generally found together in some ahundance, but perfect 

 specimens are rare, on account of their gi'oat brittleness. Many speci- 

 mens have evidently been broken and mended as the one figured in 

 Plate ^ ., fig. 2. Sucli deformities in other groups of corals have been 

 described as genera, as. for instance, Ecniesus by Philippi, and Ilemicy- 

 athus l)V iScii'uenza. 



MYCEDIUM Oken. 

 Mycedium fragile Dana. 



This species was obtained in considerable quantities in the two 

 localities named below. The greater number of the specimens were 

 dead, but an interesting series of young ones of all ages were obtained 

 (see Bulletin Mus. Comp. Zocil., No. 13, by Professor Agassiz). It is not 

 uncommon in less depth, though not often found on the reef. 



In looking over the materials in the Museum, for the detennination 

 of this coral, it has become very apparent that a revision of the group 

 is very urgent, and that proljably a large nundjer of species, and even 

 some genera, are based on very insufficient characters and ought to be 

 united. In fact, several of the specimens obtained by me in the same 

 di'edgeful, if seen separately from different localities, would mdiesitatr 

 ingly be j)ronounced different species; whilst l)eing put on guard by 

 the association, a closer examination shows that the characters vary 

 considerably, even in different parts of the .same corallum. Such are the 

 costal striic, which may be sube((ual, or alternately large and snudl ; the 

 caiicli's, wliicii may be Hat or I'aised. isolated or in rows, columella ]n'es- 

 enl or absent, etc. 



in this connection it may be renuirked that J/ycrt//H;/; /'yv/y/A', which 

 Milne-Kdwards and Ilaime think may be closely allied to Agarida xin- 

 ihilii. lias really no resemblance to that S2:)ecies at all. The latter is 

 found on the coast of Cu])a- (cabinet of Mr. R. Arango, in Havana), but 

 not in Florida, as liir as 1 am aware. 



OIl'Tortugap, in .3(; ami 13 Intlioms. 



