OF LOWER GREENS A XI) PLANTS. 301 



HORIZON. " Potton Sands," Lower Greensand ; probably 

 derived from Wealden. 



LOCALITY. Sand-pit, just outside Leighton Buzzard. 



TYPE (V. 13238). Specimen transferred to British Museum 

 (Natural History), by lioyal Agricultural College, Cirenccster, 

 1915. 



GENERAL DESCRIPTION. There are twelve more specimens of 

 this species, all found in the same deposit and all identical in 

 colour and texture, being petrified in a dark limonite, very close 

 and heavy and quite opaque in most cases where sections have 

 been attempted. Three at least of these specimens resemble 

 each other so much that it is certain that they represent parts 

 of the same individual, which must have been much longer than 

 the type-specimen, and consequently much exceeding the length 

 given in the diagnosis. 



There is every indication that the trunks were straight and 

 relatively slender, and not like the rounded massive trunks of 

 many Bennettites. The pith is very large for the diameter of 

 the trunk, but shows no sign of vascular strands within it, the 

 statement of Carruthers that it was " permeated with vascular 

 bundles" being probably due to the deceptive appearance of the 

 pseudo-concretionary matrix toward the centre, which to the 

 naked eye has an effect very similar to the central strands of a 

 Meduttosa. 



The pith measures up to 8 cm. in diameter, and is a straight 

 u n constricted mass. Externally, as is seen in specimen 47049 

 (text-fig. 94). the primary bundles and broad medullary rays 

 give rise to the lenticular ridges and groovings which are so 

 characteristic of pith-casts in this family. The tissue composing 

 the pith (see section V. 521 9 a), which is poorly preserved and 

 is generally wanting, appears to have been a uniform mass 

 of unspecialised parenchyma, in which circular cavities suggest 

 the remains of gum-canals. 



The wood is in two distinct rings, each from 5-8 mm. in 

 radial thickness and apparently formed from distinct cambiums 

 (text-figs. 94 & 95). They can be clearly recognised in the 

 broken ends of most of the specimens, even with the naked 

 eye. Owing to the opaque nature of the matrix but little can 

 be seen in microscopic section in most cases, but in the slides 

 of V. 5:219 patches show the regular radial rows of tracheids, 



