to Micro-Paleontology. 291 
the Carboniferous rocks of Redesdale, in Northumberland 
(coll. Richard Howse and H. A. Nicholson). The Arctic 
specimens (var. arctica) are from the Carboniferous rocks of 
Feilden Isthmus (lat. 82° 43! N.), and were collected by Capt. 
Feilden, as naturalist to the Nares expedition (coll. Brit. Mus.). 
3. Notes on Monticulipora ? tumida, Phill. 
The general characters and minute structure of the form 
which I regard as being the Calamopora tumida of Phillips 
have been previously described by me (‘The Genus Monticu- 
lipora,’ p. 120). After an examination of an enormous 
number of additional specimens, I have only little of structural 
importance to add to the description formerly given; but I 
should wish to make some remarks as to the affinities and 
synonymy of the species. 
Monticulipora? tumida, Phill., is an essentially dendroid 
species, but, like other ramose forms, it often begins its 
existence in the shape of a thin crust growing upon the stem 
of a Crinoid or some similar object. The stems are mostly 
between 1 and 2 lines in diameter, but may reach at least 
3 lines in diameter. The calices are rounded, oval, or sub- 
polygonal, with very thick walls, their actual apertures being 
round or oval and mostly between 9\5 and <5 inch in diameter. 
The lips of the calices are raised into prominent rims, which 
slope down by a deeply concave edge to the margin of the 
actual visceral chamber, thus giving rise in some cases to the 
appearance of perforated diaphragms at the bottom of the 
ealices; but I am satisfied that this is the true explanation of 
the appearances in question. ‘The prominent intercalicine 
ridges always support, in unrubbed examples, a row of promi- 
nent blunt spines, which can sometimes be observed to open by 
distinct circular apertures, and which give to the surface a 
characteristic rough or spinulose aspect and feel. Lastly, 
minute corallites or interstitial tubes are commonly developed 
at the angles of junction of the larger corallites, or are agere- 
gated to form distinct macule. 
With regard to the ¢nternal structure of the corallum , tan- 
gential sections (fig. 3, A) show that the walls of the coral- 
lites are completely amalgamated in the peripheral region, the 
conjoint walls being usually about 73, inch across, while the 
visceral chambers average about ;5 inch in diameter. The 
visceral chamber of each corallite is surrounded by a thickened 
fibrous layer, and the interspaces between the corallites are 
filled with clear sclerenchyma, traversed by rows of dark- 
coloured hollow spines. Minute corallites or tubuli are also 
