318 DESCRIPTION OF CHALK CORALS. 
in connection with the small swelling regarded as an indication of the true 
mouth ; also the probable nature of the central foramen. 
Of figured ascidian corals which present a central foramen, more or less 
analogous to that of Mr. Dixon’s coral, may be mentioned Eschara dubia of M. 
Milne-Edwards', Escharites incrustata of Herr Roemer’, and Vaginopora fragilis 
of M. DeFrance?® ; yet no structural agreement is believed to exist between those 
openings and the large pore of the coral under examination, the former being 
clearly more or less altered, true apertures, whereas in the present case the mouth 
is conceived to have been situated at the distal extremity of the cell. 
Though a fully satisfactory identification with Escharina could not be esta- 
blished, yet as a greater number of resemblances were noticed than with any 
other genus known to the author, it is deemed most advisable to assign the coral 
provisionally to it*. 
The only specimen which was examined, incrusted a Micraster, and part of its 
irregularities were possibly due to the nature of the subsurface. The area oc- 
cupied by it was rather more than half an inch square, the margin being to a 
certain extent quadrilateral ; but there was an evident divergence from a centre. 
The perfectly covered cells were unequally distributed, and fully as abundant 
near the boundary of the specimen as towards the middle ; they were also occa- 
sionally wanting throughout relatively large intervals, which presented only 
cavities analogous to those of Marg. elliptica, M. Velamen and M. bipunctata. 
Such of the marginal cells as exhibited apparently an early state of development 
had rudiments of a side wall, but no distinct back lamina, the small papill of 
the Micraster being quite visible: in cases a little distant from the extreme 
edge, the periphery had its full dimensions ; and proofs of a furrow and of a back 
wall were also shown. The characters of uncovered cells, whether in a supposed 
immature condition, or deprived of their exterior by abrasion, are given in fig. 8a. 
The progressive steps by which the outer covering was formed were not observed, 
but the lamina was possibly developed from the sides to the centre; or if the 
" Mémoire sur les Eschares fossiles, Ann. Se. Nat. 2nde sér. Zool. t. vi. pl. 12. f. 17 a. 
Verst. Norddeuts. Kreidegeb. p. 17. tab. 5. f. 8; not f. 10, a misprint in p. 17. 
De France, Dict. Se. Nat. t. lvi. p. 428; or De Blainville, Man. d’Actinol. p. 441. pl. 72. f. 3, 3a: 
also Michelin, Icon. Zoophy. p.176. pl. 46. f. 22 a, b. 
* Objections have been made to the word Hscharina (see Lepralia, Brit. Zoophytes, 1st and 2nd 
edits.), but as it is employed in the present case provisionally, and as the division of Celleporide, to 
which Escharina or Lepralia belongs, claims an extended investigation, the retention of the name may 
not perhaps be altogether inaccurate. 
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