DESCRIPTION OF CHALK CORALS. 289 
those of an unbroken termination on the state of development at the time the 
polype was killed’; and the actual appearance of both occasionally on the obli- 
terating effects of abrasion. Nevertheless M. Milne-Edwards’s Pust. proboscidea 
(op. crt. pl. 12. f. 2) could not, it is conceived, yield under any circumstances a 
fracture similar to that of Pust. radiciformis or of Mr. Dixon’s coral. Slightly 
worn surfaces (fig. 8b) gave fine and faint, translucent lines which formed poly- 
gonal figures more or less midway between adjacent cavities ; and they supported 
the inference that the visceral receptacles were not simple hollows in a homo- 
geneous substance. They appeared nevertheless to have resulted from animal 
secretions filling up slight interspaces ; and the small degree of translucency was 
probably due to a less proportion of mineral matter ; but perfect exteriors, or those 
which were regarded as exhibiting a mature condition, presented a continuous 
layer resembling that of M. Goldfuss’s original figures. From the preceding 
statements it would appear, that further information is requisite before a right 
opinion can be formed respecting the subordinate structures of M. De Blainville’s 
genus ; and consequently that the proposing of a new one for Pust. radiciformis 
or the English chalk fossil is inadmissible. 
Four specimens of the cretaceous coral were examined, the finest being repre- 
sented by figure 8. They varied not in the diameter of the branches, nor in the 
manner of dichotomosing; the only differences depending on irregularities of 
growth and state of preservation. A comparison with MM. Goldfuss and Miche- 
lin’s figures proved that the dimensions were similar in all the three cases. So far 
as was observed, the branching was strictly dichotomous, but the separation was 
not always in the same plane; and M. Goldfuss says his specimen had a three- 
forked division. The mouths of the visceral cavities (fig. 8 a) were fully as pus- 
tular and salient as in M. Michelin’s figure 46, and under some irregularities of 
development they projected to a still greater extent, assuming a free tubular 
character. In the ‘ Iconographie Zoophytologique’ it is stated, that, ‘‘ dans 
les échantillons bien conservés, les bords des pores sont presque tubuleux ”’ (loc. 
cit.). In what appeared to be cases of great deviation from normal productions 
(fig. 8 h), the margin was cylindrical and narrow and protruded very little; the 
apertures being closed by a solid plate. The regular mouths (fig. 8 a) were 
round or oval, and simply tubular endings, without any indications of an oper- 
culum ; they were arranged as before stated, for the greater part in annular rows, 
but very many deviations occurred. The surrounding intervals were small, and 
" Compare figure 4 J. pl. 53. M. Michelin, with figure 8 illustrative of Mr. Dixon’s fossil. 
