DESCRIPTION OF CORALS. 155 
cimen, moreover, proved that Idmonea agrees with Hornera, occasionally at 
least, in having the tubular openings on the inner side of the branch, a character, 
it is believed, not previously exhibited (for other agreements consult Dr. M.- 
Edwards’s Memoir on Hornera, &c., op. cit.). Though the distance between the 
bifurcations varied from a line to less than half a one, yet the length of the pairs 
of shoots, as respects the points of re-bifurcation, was curiously symmetrical, 
only one marked want of coincidence appearing. ‘This character nevertheless 
should be regarded possibly as of only local interest. The breadth of the shoots 
immediately after subdivision differed sometimes very slightly from that of the 
preceding entire branch ; in general, however, aslight increase of width occurred 
towards the points of divergence, and then a small difference was visible. The 
imperfect state of the oral surface frustrated any attempt to ascertain the cha- 
racters attendant on the bifurcations ; but the tubuli comprising the interior and 
back of the coral regularly inclined outwards, though a few of those along the 
line of separation appeared in one instance not to have been prolonged into 
the offsets; an operation, however, insufficient of itself to account for the 
branching *. 
The rounding of the dorsal side prevailed throughout the specimen, but the 
degree of curvature varied slightly. This surface was very generally preserved, 
and displayed relatively broad, opake white, longitudinal bands, microscopically 
punctured, forming the exterior of the outer layer of tubuli; also fine, sometimes 
slightly projecting, less opake laminz, which ranged inwards, occupying the in- 
tervals between the tubes. No trace of a distinct uniform or solid outer layer 
was noticed. In transverse sections the whole of the interior was penetrated by 
vertical, cylindrical tubuli with exceedingly thin walls, the outer series, where 
preserved, being somewhat regularly disposed, but the remainder were con- 
fusedly associated. 
The characters of the oral surface may be better gleaned from fig. 24a than 
a description. The existence of a decided crest not quite equal in breadth at the 
base to the diameter of the branch was clear ; transverse rows of tubuli could 
also be detected, though only in their abraded remains ; and one perfect mouth 
was also noticed situated at the outer or dorsal extremity of a row. It was large, 
circular, and slightly raised. 
Bath, 1846. 
* The reader is referred to Mr. Dana’s large work on Zoophytes for valuable observations on the 
bifurcation of corals (1846). 
