68 REPORT — 1853. 



the vast (and generally unconformable) inferior groups, which collectively are found 

 in Cambria, and are assuredly not found collectively in any Silurian section, are 

 still called Cambrian. 



The preceding classification places the Silurian series on its true physical and true 

 palfeontological base ; but it does exclude from that series the shelly sandstones of 

 Caer Caradoc, and the calcareous flagstones of Llandeilo. 



To confirm the preceding conclusion, the author then went on to a discussion of 

 certain sections examined (by Professor M'Coy and himself) immediately before the 

 meeting of the British Association at Hull. They were prevented from extending 

 their examination to the sections of Builth and Llandeilo by a very vexatious acci- 

 dent ; and their joint remarks, so far as they appear in this abstract, relate to sec- 

 tions at the south-west end of the Longmynd, and to sections through the typical 

 Caradoc sandstone, where it forms a well-known terrace, ranging from the banks of 

 the Onny to the banks of the Severn. 



(1.) Sections of the Pentamerus Limestone and May Hill Sandstone of Norbury and 

 Linley. — From these rocks (which rest unconformably on the old Longmynd slates) 

 they obtained the following fossils, the species determined by Professor M'Coy : — 



* Ptilodic/ya lanceolata, as at Dudley. 



* PalcBopora interstincta, common to Cambrian and Silurian. 



*Favosites multiporatus, ditto. 



*Petraia bina, as in Wenlock limestone and May Hill sandstone. 



* , unnamed species, same as at May Hill. 



*Encrinurus punctatus, common to Cambrian and Silurian rocks. 



Pentamerus loevis'] . , , . ,.,, , , 



,, Mn almost mcredible abuudance. 



— — oblongus J 



*Lept(Bna transversalis, as in Wenlock and limestone of Woolhope, Dudley, &c., 



and May Hill sandstone. 



* euglypha as in Wenlock limestone, and Dudley. 



*Orthis elegantula, common to Cambrian and Silurian. 



* pecten, ditto. 



* Davidsoni, as at Wenlock limestone of Walsall, and sandstone of May Hill. 



** Spirigerina reticularis, common to Cambrian, Silurian, and Devonian. 



* Litiorina octavia, as in Wenlock limestone. 



Upon this list it is remarked, that out of fifteen species eight have not yet been 

 found, except in the Wenlock group or its equivalents ; and that of the remaining 

 seven species, one ranges through both the Silurian and Devonian series, while the 

 other six belong to species already known to be common both to Cambrian and Silu- 

 rian rocks. On the other hand, all the types hitherto regarded as exclusively cha- 

 racteristic of Cambrian rocks are wanting. Hence the author (along with Professor 

 M'Coy) arranges the Pentamerus limestone, &c. of Norbury at the base of the Wen- 

 lock group, and cuts it off from the Caradoc sandstone. He further remarks, that 

 those fossil species which are admitted to be common to the Cambrian and Silurian 

 rocks, appear chiefly to abound in the uppermost beds of the Cambrian series ; as 

 also in the May Hill sandstone, which is the true base of the Silurian series. In other 

 ■words, the common species abound in the very beds where we should expect to find 

 them. 



(2.) Section of the Onny in descending order. — The lower parts of the river banks 

 were under water during the author's visit to the country along with Professor 

 M'Coy ; but the following facts were partly supplied by excavations which had been 

 kindly made, at the author's request, by Mr. Duppa of Cheyney Longville, in places 

 out of the reach of inundation. 



In the first excavation, 200 yards above Stretford Bridge, abundance of the fol- 

 lowing fossils :— 



Graptolites Ludensis. Calymene tuberculosa. 



Odontochile longicaudata. Cardiola interrupta. 



Between this locality and the following is a change of surface, and no rock is 

 distinctly seen for some hundred yards. This is the place where we might expect 

 the May Hill sandstone and Pentamerus limestone. 



About 300 yards above Longville Bridge the following fossils ate abundant, with' 

 out intermixture of the above-named species : — 



a 



