to Micro-Paleontology. 289 
small dark spots marking the presence of spiniform processes 
or small tubuli. Very commonly, however, there are seen at 
the angles of junction of the corallites large, round, very thick- 
walled tubes, each with a central dark spot or a minute 
median opening. It is difficult to be certain what these 
eircular thick-walled tubes may be; but they are very cha- 
racteristic of most tangential sections of S. Howsi, and they 
perhaps represent a special series of corallites. On the other 
hand, if the section traverse the thickened nodes of the coral- 
lites (as in fig. 1, B, and in Pl. X. figs. 7 and 8), the tubes 
appear to be thick-walled, and we observe in general the 
following objects :—(1) the oval or circular apertures of the 
ordinary corallites, some of these being occupied by the ring- 
like perforated tabule ; (2) the apertures of small interstitial 
tubuli, either scattered here and there (Pl. X. fig. 8) or 
ageregated into “macule” (Pl. X. fig. 7); (8) numerous 
irregularly distributed dark spots in the walls of the corallites, 
which often exhibit a minute clear spot in the centre, and 
which are doubtless the sections of hollow spines; and (4) 
large circular thick-walled tubes, such as have been previously 
alluded to, which present a central dark spot or clear space, 
and usually a well-marked dark margin (PI. X. fig. 6). 
As regards the affinities of Stenopora Howsti, it is most 
nearly allied to S. tasmandensis, Lonsd.; but the latter is 
easily distinguished by the smaller number and much larger 
size of its spiniform tubes, and by the fact that the tabulee of 
the peripheral region are few in number, and, so far as my 
observations have gone, imperforate. ‘The form, however, 
which it is most difficult to separate from S. Howsti is that 
which has been generally recognized as Monticulipora (?) 
tumida of Phillips; but before discussing this point I may 
briefly describe a remarkable form of S. Howsi from the 
Arctic regions. 
2. Stenopora Howsii, var. arctica, Nich. 
There exist in the magnificent collection of the British Mu- 
seum several specimens of a large Stenopora from the Car- 
boniferous rocks of Feilden Isthmus, which were collected in 
the Nares expedition. By the kindness of my friend Dr. 
Henry Woodward, F.R.S., [ have been permitted to examine 
these specimens, and at once satisfied myself as to their sub- 
stantial identity with the Stenopora Howsdi of the Carbonite- 
rous rocks of Northumberland. They exhibit, however, 
certain subordinate points of distinction from the British types, 
and I think it best therefore to mark the existence of these by 
the addition of a varietal name. 
