TRANSACTIONS OF SECTION C. 653 



Ludlow to the bottom of the Wenlock series, and although Ni'matophycns has not 

 occurred in so many beds or has escaped my notice, it has exactly the same range, 

 as I have found it in the tiip of the Ludlow and at the base of the A\'enlock and in 

 a considerable number of intermediate beds ; still it is only in two beds in Tymawr 

 Q.uarry that I have found the two species in question preserved in a state which 

 allowed of transparent sections being made. The lowest bed is a muddy sandstone, 

 full of Rhynchonella Stricldandi, and the other being a thin parting on the top of 

 the Ctenodonta sandstone of SoUas, and about 10 feet above the Rumney grit. 

 The specimens from the last bed being much superior to the lower one, I will only 

 deal with it. 



This bed is only from 1 to 2 inches in thickness, and contains large numbers 

 of Discina ruijata, of LiiKjula two species and a large Orhicula with casts of 

 branching Zoophytes of a species not known to me ; it is wholly of a marine 

 character, and at a point west-south-west becomes of a concretionary character, 

 every little nodule of which when broken open shows a fragment, or a whole, 

 Lingula, Discina, Conularia, or other shell ; the whole bed is highly impregnated 

 with iron, which rapidly oxidises when broken and exposed to the atmosphere, 

 and the difficulty is to understand how perhaps the most mineralised bed of the 

 section should contain the best preserved specimens of these organisms. 



When preserved in mudstone the Pachytheca and Nematophycus do not display 

 any minute structure, the form and general appearance being the only points to 

 be recognised. 



When preserved in limestone the carbonaceous character is most readily 

 noticed, but the microscopic details are not very perfect ; its resemblance to fragments 

 of drift-wood is very striking to the naked eye or when a hand lens is used. 



When preserved in concretioimry nodules the outer wall is usually perfect, but 

 the cellular structure of the interior is reduced to a pocket of carbonate of lime or 

 oxide of iron. 



There are undoubtedly two totally distinct organisms known at present as 

 Pdchytlieca spJia-rica ; one of which is a perfectly spherical body, variable in size 

 like the Pachytheca and like it consisting of a more compact outer layer and a less 

 dense centre, but, however thin this is cut, it never contains any internal structui'e, 

 showing only a chitinous-like appearance, with sometimes a fungous-like growth 

 on the exterior; this, I think, is no doubt the eg^ of a crustacean, more especially 

 as Pteroyotus has been found in this quarry and in a section of the same beds. 

 Yesterda^Y, a member picked up a specimen which may likely turn out to be a 

 fragment of Slimonia. 



Pachytheca may be described as a thick -walled globular rind of tubular 

 tissue, with small intertubular spaces enclosing a small cavit}' of much looser 

 and more branched tissue, coral-like in appearance, which is in continuous struc- 

 tural connection with the radiating thick-walled, slightly branched and rather 

 densely packed tubes of the exterior, the intertubular spaces in the exterior portion, 

 as seen in transverse section, being small in comparison with the intertubular 

 spaces found in Nematophycus. I have examined large numbers of Pachytheca to 

 see whether any hilum or point of attachment was present, and have never seen 

 any indication either on the external wall or in the internal structure of any such 

 as might be reasonably expected to show some differentiation, were there any 

 ground for belie^ing that it was either a fruit of a conifer, or the conceptacle or 

 even one of the floats of a seaweed like sargassum or ficcus. 



Nematophycus occurs principally in small fragments, waterworn and irregular 

 in shape and never over an inch in length, and in only one specimen have I found 

 any appearance of branching ; in this case it was a small stem from the Discina 

 bed about 5-inch in diameter, rather oval in section and with one branch of barely 

 •J-inch diameter and a |-inch long, which was again forked at the extremity, the 

 branchlets being about j'^-inch in length and nearly the same in thickness. The 

 tissue of the outer part of the stem was slightly differentiated from the interior, 

 but essentially the structure was the same, and the apparent difference may have 

 been more dependent on the different degree of oxidisation of the iron in the 

 weathering of the fossil tlian anv bark-like difference of structure. 



