R. P. Whitfield—Structure of Dictyophyton. 53 
Art. X.— Observations on the Structure of Diclyophyton and tts 
affinities with certain Sponges ; by R. P. WHITFIELD. 
In the Chemung group of New York, and in the Waverly 
beds of Ohio and elsewhere, there occurs a group of fossil 
bodies which have been described under the name Dictyophyton, 
but the nature of which I think has not been properly under- 
stood. In the 16th Report on the State Cabinet of Natural 
History of New York, page 84, in the remarks preceding the 
generic description, they are referred to the vegetable kingdom 
with the opinion pupae “that they are Alge of a peculiar 
form and mode of growth.” A reference which I think their 
nature does not warrant. 
If one examine the figures of the various species waaay 
given on Plates 8 to 5A of the above cited work, it w 1 be 
seen that these bodies are more or less elongated tubes, otraight 
or curved, cylindrical or angular, nodose or annulated ; and 
that they have been composed of a thin film or pellicle of net- 
work, made up of longitudinal and horizontal threads which 
cross each other at right angles, thereby cutting the surface of 
the fossil into rectangular spaces ; often with finer peter 
hen 
between the coarser ones. W the specimens, which a 
casts or impressions in sandstone, are carefully examined, it i is 
found that these threads are not interwoven with each other 
like basket work, or like the fibers of cloth, nor do they ante 
with each other as do vegetable substances ; but one set 
appears to pass on the outside, and the other on the inside of 
the body. The threads composing the net-work vary in 
strength, and are in regular sets in both repeals while the 
entire thickness of the film or substance of the ody has been 
very inconsiderable. In one species, the only one in which 
the substance filling the space between the cast and the matrix 
has been observed, it appears to be not more than a twentieth 
of an inch in thickness, and is ochreous in eagen si This 
eculiar net-like structure does not seem to be that of any 
nown plant, nor does their nodose, annulated, Ricca O38 or 
often sharply longitudinally angular "form, with aera) perfect 
corners, indicate a vegetable structure; moreover, it is not a 
feature likely to be retained in a soft, yielding Repetasis body 
of such extreme delicacy and large size, while drifting about 
by the action of water, in becoming imbedded in the sand of a 
sea bottom, but would rather were a substance of consider- 
able rigidity and firmness of tex 
In examining the structure of Bapleietis it is found to be 
composed of longitudinal and horizontal bands similar to those 
above described, with the additional feature of sets of fibers 
