212 Mr. R. Etheridge and Dr. H. A. Nicholson 
the first to notice the important character of the perforated 
walls; and they also remarked on the supposed septal system, 
with the absence of tabule and a columella. The next step, 
the double demonstration by Von Seebach of the identity 
of Paleacis and Sphenopotertwm, on the one hand, and of the 
species P. cunetformis, J. Haime, with S. cuneatum, M. & W., 
was a most important one. He also confirmed Milne-Kd- 
wards’s reference of Palwacis to the Madreporaria Perforata. 
Admitting the Ptychochartocyathus laxus, Ludwig, to be a 
Paleacis, we find that Ludwig improved our knowledge of 
the supposed septal characters, and noted the presence of what 
he termed a basal concentric epitheca. Dr. Kunth confirmed 
the presence of the mural pores originally noticed by Meek 
and Worthen, and further showed that these pores led into a 
series of canals traversing the substance of the corallum, and 
placing the cups in connexion with one another. He likewise 
disputed the presence of any true ccenenchyma as supposed by 
Milne-Edwards, and left the matter of a columella an open 
question. Lastly, Prof. de Koninck confirmed Kunth’s re- 
marks on the mural pores of Paleacis, determined the absence 
of a columella, and supported Kunth’s reference to the Eu- 
psammide. We also believe De Koninck was the first to refer 
Hydnopora? cyclostoma and Astreopora antiqua to the genus 
Paleacis. , 
2. Description of, and Observations on, the Genus. 
Genus Patmacis (J. Haime), M.-Edw. 1860. 
Hydnopora, Phillips, Geol. York. 1836, ii. p. 202. 
Astreopora, M‘Coy, Synop. Carb. Foss. Ireland, 1844, p. 191; Morris, 
Cat. Brit. Foss, 1854, 2nd ed. p. 47. 
Paleacis (J. Haime), M.-Edw. Hist. Nat. Corall. 1860, iii. p. 171. 
Sphenopoterium, Meek and Worthen, Proc. Acad. Nat. Sci. Philad. 
(for October 1860), p. 447; iid. Illinois Geol. Surv. Rep. 1866, ii. 
p. 145, i : 
Paleacis, Von Seebach, Nachr. d. k. Gesell. d. Wissensch. zu Gott. 1866, 
p- 240; id. Zeitsch. d. deutschen geol. Gesell. xviii. 1866, p. 308. 
? Ptychochartocyathus, Ludwig, Paleeontographica, 1866, xiv. pp. 189, 
231 
Paleacis, Kunth, Zeitsch. d. deutschen geol. Gesell. 1869, xxi. pp. 186, 
187 ; De Koninck, Nouv. Rech. Anim. Foss. Terr. Carb. Belgique, 
1872, pt. 1, p. 154. 
Gen. char. Skeleton more or less cuneate or irregularly 
turbinate in form, depressed, or with age becoming irregular, 
adhering, on the one hand, by the whole or part only of a 
concentrically wrinkled base, or, on the other, by a small 
peduncular extension of the skeleton. Cups variable in num- 
ber, one to twelve and perhaps more, cell-like, opening up- 
