280 Dr. H. A. Nicholson and Mr. R. Etheridge, Jun., on 



the Lower Silurian genus Columnopora, Nich., which it nearly 

 resembles in form and habit. It is distinguished from the 

 latter, however, by the less regularly perforate character of 

 its walls, by the rudimentary condition of its tabular, and by 

 the irregularly dividing and trabecular septa. We are unable 

 to institute any comparison between Arceopora and the Cre- 

 taceous genus Komnckt'a, E. & H. ; but the septa of the latter 

 seem to be merely spiniform (six in number), and the tabular 

 are said to be well developed and complete. 



Locality and Horizon. Limestone of the Burdekin River, 

 N. Queensland. Devonian. 



Collector. The late R. Daintree, Esq. 



Genus PACHYPORA, Lindstrom. 



Pachypora meridionalis, Nich. & Eth., Jun. 



Spec. char. Corallum ramose, of cylindrical branches, about 

 two lines and a half or three lines in diameter, dividing dicho- 

 tomously at comparatively remote intervals. Corallites not 

 regularly polygonal, with very thick walls, the diameter of 

 which increases as the mouth is approached. Calices hardly 

 at all oblique, about a third of a line, or sometimes rather more, 

 in diameter, oval, rounded, or irregular in shape, often open- 

 ing into one another, surrounded by thick obtuse margins, 

 which exhibit no traces of the original polygonal wall of the 

 corallite. Mural pores few, very large, and irregularly placed. 

 Tabulae few and remote. 



Obs. This species is unquestionably very closely allied to 

 Pachypora (Favosttes) cervicomis^ De Blainv., of the Euro- 

 pean Devonian ; and we have felt some hesitation in giving 

 it a distinct specific designation. Both belong to that section 

 of Favosites in which the walls are thickened by the secon- 

 dary deposition of sclerenchyma in successive laminaB, the 

 amount of this thickening being increased as the mouth is ap- 

 proached; and both are therefore referable to Lindstrom's 

 genus Pachypora. Both are alike in form and general habit, and 

 have singularly large, sparse, and irregular mural pores. After 

 a comparison, however, of the Australian specimens with ex- 

 amples from the Eifel, both macroscopically and microscopi- 

 cally, we have come to the conclusion that the former must 

 in the meanwhile be regarded as specifically distinct, upon the 

 following grounds : — 



a. Pachypora meridionalis, nobis, is, on the whole, a much 

 smaller species than P. cervicornis, De Blainv., the branches 

 in the latter often reaching 8 or 10 lines in diameter. 



b. The corallites in P. cervicornis can always be shown, by 



