696 Professor Sedgwick and R. I, Murchison, Esq., on the 



hardly avoid surmising that the peculiar plants of the "^ terrain d'anthracite 

 inferieur" of Professor Voltz, and those of a supposed similar age in Brit- 

 tany and other parts of France, may eventually be found to be on the same 

 parallel with this portion of our North Devon series. 



3. Inferior Groups of the North Devon Section. — The number of fossils 

 hitherto collected is far too small to justify us in affirming to what extent the 

 fossils of the Ilfracombe calcareous slates (North Devon Section, No. 3.) differ 

 from those of Barnstaple. A few species are certainly common to both, among 

 which we may quote two species oiLeptcena and a Pecten (see the list). Corals 

 abound in the Ilfracombe slates, though the species are not numerous. The 

 Favosites polymorpha (never yet discovered in the mountain limestone, or 

 below the upper Silurian groups,) is the most abundant. With it is another 

 entirely new species, which also abounds in the Cornish fossiliferous strata 

 beneath the culm-measures. On the whole we may state, on the authority of 

 Mr. Lonsdale (from whom alone we have derived any accurate information 

 on this head), that the Devonian corals are all either of species peculiar to 

 these groups or such as occur only in the higher part of the Silurian system. 



Immediately below the Ilfracombe calcareous slates, are some hard strong- 

 beds, with numerous impressions of a large cordiform bivalve, unlike any- 

 thing we remarked in the overlying beds. From the lowest group of all (North 

 Devon Section, No. 1.) we have very few well-preserved fossils : among them 

 are many beautiful casts of a Fenestella, and among the bivalves is an Orthis 

 of a new species, and a Spirifer identical with one found near Barnstaple (Spi- 

 rifer attenuatus ?). 



Such is the summary of the evidence given by the fossils of the North Devon 

 section ; and imperfect as we acknowledge it to be, we think it sufficient to 

 bear out our proposed classification ; esj)ecially as we know of no conflicting- 

 fossil evidence that is in any way opposed to it. 



3. South Devon and Cornwall. — In the comparison of the mineralogical 

 groups of North and South Devon, we can add nothing to what has been stated 

 in a former paper. We could not bring the great upper South Devon limestone 

 into direct comparison with the calcareous zone of Barnstaple ; because, in that 

 case, the great slate formation, which overlies the Plymouth limestone, would 

 have no representative in North Devon We therefore provisionally placed 

 the great calcareous group of South Devon on a parallel with the lower fos- 

 siliferous groups toward the northern extremity of our section. The fossils 

 appear on the whole to bear out this classification. 



First, then, as to the South Devon corals. — None of them have been found 

 in the mountain limestone, several are new or not known to occur in the Si- 



