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On the Structure of Sigillaria scutellata, Brongn., and other 
Kusigillarian Stems, in Comparison with those of other 
Paleozoic Lycopods. 
By E. A. NEWELL ArpeEr, M.A., F.LS., F.G.S., Trinity College, Cambridge 
University Demonstrator in Paleobotany, and HucH H. Tuomas, B.A., 
formerly Scholar of Downing College, Cambridge. 
(Communicated by D. H. Scott, F.R.S. Received November 8,—Read 
December 5, 1907.) 
(Abstract.) 
Petrified stems belonging to the genus Sigilaria have hitherto proved to 
be extremely rare in the Upper Carboniferous rocks. The present paper 
contains the first full account of the structure of the Eusigillariz or ribbed 
Sigillarias of the Rhytidolepis section. Hitherto our knowledge of the 
anatomy of such stems has been limited to the account of the bark given by 
Williamson, and to brief descriptions of specimens, including the vascular 
cylinder, by Professor Bertrand and Dr. Scott. i 
The material, which forms the basis of the present study, consists of 
a petrifaction from the Lower Coal Measures of Shore-Littleborough in 
Lancashire, containing two well-preserved stems, lying side by side. 
The external surfaces of the ribs of both stems have been exposed by 
Mr. James Lomax, after much difficulty, and our thanks are due to him 
for his skill in preparing the sections. The characters of the ribs agree with 
those of the impressions known as Sigilaria seutellata, Brongn. 
In addition, other stems are described in which the ribs are not exposed, 
and which cannot, therefore, be determined specifically. Radial and tangential 
sections through the bark of all these specimens show, however, that they 
belong to species of the Rhytidolepis section of the Eusigillaric, which, like 
Sigillaria scutellata, possessed distant leaf scars. These additional petri- 
factions agree exactly with Sigillaria scutellata, and have been made use of 
to illustrate further the anatomy of that species. 
The stele has a well-marked pith, a tissue which is not, however, preserved 
in any of the stems which we have examined. The medullary cavity is 
bounded by a continuous ring of scalariform tracheides,—the primary 
wood,—the outer margin of which is crenulated. The protoxylem elements 
lie at the apices of the blunt, rounded teeth of the corona. The elements of 
the protoxylem and primary wood appear to consist entirely of scalariform 
tracheides. The elements of the secondary wood are also scalariform, and 
