BRITISH ASSOCIATION MEETING. 



485 



Abstract of a Paper " On some Eishes and Tracks from the Passage- 

 rocks, AND FROM THE LoWER ReD SaNDSTONE OF HEREFORDSHIRE." By 



THE Rev. W. S. Symonds, E.G.S. 



]VIr. Symonds, in this paper, called upon Sir Roderick Mnrchison to make 

 greater allowances than he had hitherto seemed disposed to do for the appear- 

 ance of fish in the Lower Ludlow rocks of Leintwardine, Herefordsliire. This 

 fish, the Fteraspis Ludensis (Salter), was not found as Sir R Murcliison seemed 

 disposed to regard its discovery, in strata a few feet below the original upper 

 Ludlow "bone-bed," but in the Lower Ludlow deposits, with the whole thick- 

 ness of the Upper Ludlow shales and Aymestry rock intervening. There was 

 no doubt of the fact that fish-life must now be immensely ante-dated, even since 

 the publication of Sir R. Murchison's last edition of his work upon Siluria. 



Mr. Symonds called the attention of the audience to a collection of fossils 

 showing the gradation of the Pteraspis from the Lower Ludlow rocks, through 

 those passage- or transition-rocks which lie between the upper Silurians and the 

 Old Red sandstone, into the central Old Red rocks of Herefordshire. The 

 species were different, but the genus was the same. Stereoscopic plates were 

 exhibited of a large slab of Old Red sandstone wliich was rippled by the waves 

 of the ancient Old Red sea, and scored deeply by some Old Red iish or crus- 

 tacean wliich had wended its way over a shallow beach or sandy shore. The 

 slab was obtained by the late Rev. T. T. Lems of Aymestry, the friend and 

 coadjutor of Sir R. 1. Murchison, and who at his death left it to Mr. Symonds. 



On the Origin of the Structure called Cone-in-Cone, by H. C- 



SORBY, P.R.S., &C. 



Cone in Cone is met with in so many stratified rocks, that most geologists 

 must be familiar with its general characters. No one, however, appears to 

 have thoroughly investigated it ; or to have given any very satisfactory explana- 

 tion of its origin. The cones often occur in bauds parallel to the stratification 

 of the rock, their apices starting from a well defined plane ; and, after extending 

 upwards or downwards for a greater or less distance, with their axes perpen- 

 dicular to the plane of stratification, they end in bases parallel to the stratifi- 

 cation, but not all at the same exact level. They are not perfect cones, but 

 are of such forms as would result from the varied interference of surrounding 

 cones, and from the development of others within their own substance. On 

 examining thin, transparent sections with a low magnifying power, under polar- 

 ized light, the author had been able to ascertain that this peculiar structure is 

 intimately connected with some kmds of oolitic grams. Li the formation of 

 oolitic grains small prismatic crystals were deposited round a centre-nucleus, 

 radiating to all sides in nearly the same amount, so as to give rise to irregidar 

 ovoid bodies ; whereas, in the formation of cone in cone, very simdar crystals 

 were deposited almost entirely on one side, along the line of the axes of the 

 cones, in such a fan-shaped manner as to give rise to their conical shape. In 

 the thin sections of some specimens prepared for examination, every connecting 

 link between imperfect oolitic grains and genuine cones can be seen to great 

 advantage with polarized light. The growth of the cones did not, however, 

 proceed without interruption, for other smaller fan-shaped groups were developed 

 within the larger ; and thus by the mutual interference of contiguous groups 

 and of others contained within themselves, there was formed a mass of irregular 

 cones inclosing other cones. "We must therefore conclude that this structure 

 is one of the pecuKar forms produced by concretionary crystalization after the 

 deposition of the rock. 



VOL. II. 



Y Y 



