EQUISETITES. 61 



sand, which separates the carbonaceous surface of the sheath from 

 the coaly film on the surface of the main cast. 



Scarborough. Purchased. 



40,561. Text-fig. 3. [Also in Zigno (56), pi. iii. fig. 3, and 

 Seward (98), p. 275, fig. 63.] 



There are fragments of several imperfect specimens lying on the 

 shale; the best example, which is shown in the figure, measures 

 11 -2 cm. long and 1-2 cm. in breadth, the internodes having 

 a length of 4'5 cm. Portions of leaf-sheaths with short teeth 

 are faintly indicated at the nodes, and distinct impressions of 

 diaphragms occur above the nodal lines. The long slender 

 appendages, of a light - brown colour, which were formerly 

 described as leaves, are no doubt delicate branches comparable 

 to the finer branches of some of our recent Horsetails. No 

 trace of nodes can be made out on the surface of the branches, 

 but the preservation is far from perfect. A somewhat similar 

 specimen from the Yorkshire coast, with traces of branches, may 

 be seen in the Leeds Museum. 



10,379. PI. XIX. Fig. 4. 



An isolated nodal diaphragm, showing a central flat area and 

 slightly convex radiating bands of carbonized tissue separated from 

 one another by spaces. These diaphragms are usually about 1 cm. 

 in diameter, and have the form of a shallow saucer. Part of 

 a similar diaphragm is seen in Fig. 4, lying immediately above the 

 lower leaf-sheath. 



The example represented in Fig. 4 (from the York Museum) 

 shows the leaf-sheaths and linear acuminate segments very clearly ; 

 it is interesting also as being larger than many of the specimens 

 of the Equisetites lateralis type, and serves to connect the wider 

 E. columnaris with the narrow branches usually identified as 

 E. lateralis. 



The diaphragm of the specimen represented in PI. XIX. Fig. 5 

 is surrounded by a portion of a leaf-sheath, and affords good 

 evidence in support of the nature of the isolated circular discs, 

 which were considered originally to be the scars of branches. 



V. 89. Two pieces of stems on which the surface features of 

 the leaf-sheaths are clearly preserved ; on the flat or slightly 



