22 J. W. Dawson on Paleozoic Rhizocarps. 



ago by the late Prof. Hartt, and which, like Mr. Derby's speci- 

 mens, occurred in beds holding Spirophyton, though these were 

 at that time regarded as Carboniferous. In a note prepared for 

 Prof. Hartt, but not, so far as I am aware, published, I had 

 noticed these fossils as follows : — 



" Sporangites — Specimens from a shale at Rio Tapagos, above 

 Haituba. These are spore-cases, probably of a Lepidodendroid 

 plant, and appear similar to those described by Carruthers as 

 found in cones from Brazil, referred by him to his genus Flemin- 

 gites* Carruthers' specimens were from Rio Grande du Sul, and 

 were found in shales associated with beds of coal, and be- 

 lieved to be of Carboniferous age, though the fossils leaves 

 found with them and attributed to the genera Noeggera- 

 thia and Odontopteris would, if interpreted by North American 

 analogies, he supposed to be older than the true coal-formation. 

 The present specimens are labelled as Carboniferous, but the 

 occurrence in them of abundant fronds of Spirophyton rather 

 points to a Devonian date." 



Mr. Derby's spec'.m.ns contain Spirophyton, and also minute 

 rounded Sporangites like those obtained by Prof. Hartt. But 

 they differ in showing the remarkable fact that these rounded 

 bodies are enclosed in considerable numbers in spherical and oval 

 sacs, the walls of whieh are composed of a tissue of hexagonal 

 cells, and which resemble in every respect the involucres or spore- 

 sacs of the little group of modern acrogens, known as Rhizo- 

 carps, and living in shallow water. More especially they resemble 

 the sporocarps of the genus Salvinia. This fact opens up an 

 entirely new field of investigation, and I would now proceed to 

 describe these interesting specimens, to inquire as to their probable 

 affinities with modern plants and their probable relations to other 

 palaeozoic forms of vegetation found with them. 



Mr. Derby's specimens are labelled as from Rio Trombetas and 

 Rio Curua. They occur in two kinds of matrix. One is a thinly 

 laminated sandy shale, tinged red with peroxide of iron, and with 

 occasional ferruginous laminae. In this the spore-sacs are flat- 

 tened and black, and show the structure of the walls under the 

 microscope. The contained macrospores, when visible, appear as 

 minute tubercles or sometimes as depressions on the wall of the 

 envelope, or more frequently as round light-coloured spots, accord- 

 ing to their state of preservation (fig. 1 a). The other kind of 



