MADREPORA, Di 
appears to me to belong here. It consists of only the apical portion of a colony in which 
the branches are slender and the majority of the radial corallites are tubular. A small 
specimen of this form in the Berlin Museum bears the name Porites cristata, Ehrb., on the 
label. No species appears, however, to have been described by Ehrenberg under that name. 
Other specimens have thicker branches and are more arborescent in habit, and lead up 
to the forma cervicornis. 
C. Forma cervicornis. 
Corallum erect, arborescent, frequently 60 cm. or more in height and 30 to 70 em. broad. 
Base sometimes a simple dilatation of the stem, at others broad and incrusting. In certain 
specimens the whole colony forms an incrustation over dead coral, and only the distal 
branches are entirely produced by the new colony. In such specimens it frequently happens 
that the incrusted branches are blunt at the apex, and no axial corallite is distinguishable. 
At a later period, when independent growth commences, one of the corallites, situated 
about the centre of the rounded apex, increases gradually in size, and becomes the axial 
corallite of the branch in its further extension. This accounts to a great extent for the 
marked variation in size of the axial corallites, and forms an important link between this 
variety and forma palmata. Stem 2 to 4 cm. thick, or, in exceptional cases, 5 cm. 
Branches elongate and spreading, sometimes almost at right angles, but different specimens 
vary considerably in this respect; they are round, gradually tapering, 1°3 to 2, rarely 4 cm. 
thick, usually not much divided, and sometimes simple when 19 cm. in length. Near the 
periphery of the colony a few short branchlets occur, 1:5 to 3°5 em. long and about 1 cm. 
thick ; frequently two or three occur close together. Axial corallites cylindrical, normally 
4 to 5 mm. thick, and frequently 6 to 8 mm. exsert ; wall thick and very porous, strongly 
striate externally. Primary septa well-developed and subequal, second cycle more or less 
prominent. It also appears from Agassiz’s figures (‘Florida Reefs,’ pl. xviii.) that in the 
axial polyp the cycles of large and small tentacles are very distinct, but the difference is not 
so marked in the radial polyps. Radial corallites rather crowded and more or less appressed 
near the apex of a branch, but more spreading and usually a little more distant below, from 
13 to 16 in 5 cm. Immersed corallites are rare, excepting in the basal parts of the 
colony. The form is chiefly tubo-nariform in the younger parts and nariform below, where 
the thickening of the sclerenchyma has covered the tubular base ; length 2 to 5 mm., diameter 
1:7 to 2°7 mm., but adjoining corallites are subequal, and the longest ones are usually situated 
near the apex. In some specimens nearly all the radial corallites are nariform, in others a 
few have a rather elongate lip. Wall firm and a little thickened, but quite porous, becoming 
much thickened and even keeled with age. The directive septa are broad, the others usually 
narrow. Corallum porous, surface spongy and echinulate; wall strongly striate and 
echinulate. 
A specimen from Hayti, in the Strassburg Museum, differs from the majority of 
specimens which have come under my notice in having the whole corallum, including the 
