584 Benson.—Mazocarpon or the Structural Sigillariostrobus. 
only tallies with the figures given by Zeiller 1 and by Kidston, 2 but it 
explains the fact of a line like a midrib appearing on the adaxial and noton 
the abaxial surface. It is shown that in Mazocarpon a deep groove occurs 
on the adaxial surface, but that the abaxial surface is uniformly smooth and 
shows no rib. 
It is unexpected agreement in peculiarities such as this that makes one 
feel confident one is describing the same thing. 
d and e. Peduncle and its sectional form. Both Mazocarpon and the 
various species of Sigillariostrobus described are pedunculate (Fig. 10). 
The peduncles, moreover, are deciduous, and Kidston remarks 3 that this 
seems to be the normal condition in Sigillaria. The section area of the 
peduncle and cone-axis in Mazocarpon is hexagonal, and those of M. Shorense 
have the form and size of the scar which has been attributed to the cone 
in Sigillaria mamillaris. 
3, The Microsporange. 
It is of especial interest to refer here to a specimen of Sigillariostrobus 
from the Lower Coal Measures of Yorkshire, which has been figured and 
Text-fig. 4, A and b. Reconstruction of parts of the mega- and microsporangial cones of 
Mazocarpon ( Sigillaria) showing the relative size and form of the sporangia. The presence of abortive 
sporophylls is indicated above the megasporophylls in a, and below the microsporophylls in b. 
Some of the sporophylls on each cone are represented in section, the cut surface being hatched. 
Both structural and incrustation material has been utilized in this diagram. For complete incrusta¬ 
tions of cones of Sigillaria the works of Zeiller and Kidston should be consulted, a represents the 
upper part of a megasporangial cone; B represents the lower part of a microsporangial cone. 
described by Kidston 4 in his above-mentioned work. The cone is of the 
same geological age as Mazocarpon . The sporangia, regarded by Kidston 
1 Zeiller, loc. cit., Fig. 5, Plate XII. 2 Kidston, loc. cit. 
3 Kidston, loc. cit., p. 56. 4 Kidston, loc. cit., Plate II, Fig. 1. 
