Monthly Mi ical 
166 PROGRESS OF MICROSCOPICAL SCIENCE. | "journal, Sept. 1, 1870. 
a similar structure. Mr. Carruthers then described this group as a 
distinct genus, restricting it to the typical species D. ramosus, and its 
allies; and at the same time, from an examination of British speci- 
mens, he dissented from Hall’s conclusion as to its structure, which 
he considered to be exactly similar, in its proximal portion, to Diplo- 
grapsus. He has already expressed the opinion that “in D. ramo- 
sus, the hydrothece appear to have the same structure as in Climaco- 
graptus,” and he endeavours to show that, so far as can be judged from 
the imperfect state of preservation in which our British specimens are 
found, not only this species, but the entire genus, although frequently 
somewhat similar in the form of its hydrothece to Diplograpsus, is, 
nevertheless, more nearly allied to Climacograptus. This he does in 
the description of some species in the ‘ Geological Magazine’ for 
August. 
A New Photometer.—A photometer, invented by M. Nagant, is 
based upon the formation of a column of liquid, partially opaque, 
which may be drawn ovt until the length is such that the light from 
an illuminating body ceases to be visible through the liquid. The 
length of the column, which completely obscures the light, starting 
from the point where the column is thinnest, gives a measure of the 
intensity of the light under examination. 
Paleocoryne, a New Fossil Hydrozoon.—This, which is a genus of 
Tubularian Hydrozoa, from the Carboniferous formation, is fully de- 
scribed by Dr. P. M. Duncan, F.R.S., and H. M. Jenkins, F.G.S., in 
the ‘Philosophical Transactions’ for 1869. The remarkable little 
organism which forms the subject of this paper was obtained from 
the lower shales of the Carboniferous Limestone series of Ayrshire 
and Lanarkshire, so rich in fossil Brachiopoda, Polyzoa, Crinoidea, 
and Madreporaria; and was found attached to the margins of the 
polyzoarium of Fenestelle, and also in a detached and more or less 
fragmentary condition amongst the small pieces of broken Polyzoa 
and Crinoid stems which compose the fossiliferous layers of the shales. 
The base of Palwocoryne was expanded, giving rise to a short robust 
and cylindrical stem fluted and punctated on its surface, and sur- 
mounted by the body of the polypite from the upper margin of which 
radiate a single whorl of long and slender tentacles. On the upper 
surface of the body, a crateriform process, with an opening on its 
apex, indicates the position of the mouth. Its external investment 
appears to have been calcareous, covering the whole of the hydrozoon, 
except at the opening for the mouth and the terminations of the 
tentacles, which had probably ciliated ends projecting beyond the 
periderm or polypary. This is an almost solitary instance of a 
hydrozoon having a hard periderm, save the recent genus Bimeria, 
discovered on the west coast of Ireland by Dr. T. Strethill Wright. 
The Zoological position of the fossil is amongst the Hydrozoa in 
the order Tubularide, and near the Eudendride. Two species are 
described and figured by the authors, Palcocoryne Scoticum and P. 
radiatum. 
‘Regeneration of Bone by Periostewm.—M. Ollier’s recently reported 
cases seem to prove the fact of regeneration of the bones through the 
