Dr. J. W. Gregory — The Age of the Morte Slates. 59 



These seem to show that the beds here belong to the Oxynotus or 

 Armatus zones. 



South of this great cutting the line runs on an embankment for 

 some distance, and there are no exposures till we get to Willoughby ; 

 from which point southwards the sections have been examined by 

 Mr. H. B. Woodward, and will be described by him in the second 

 part of this paper. 



11. — On the Age of the Morte Slate Fossils. 

 By J. W. Gkegory, D.Sc, F.G.S. 



AS the discussion at the Geological Society on Dr. Hicks' paper 

 " On the Morte Slates and Associated Beds in North Devon 

 and West Somerset" (Quart. Journ. Geol. Soc, vol. lii, pp. 254.-272, 

 pis. X, xi) showed that the case for the Silurian age of those beds 

 rested mainly on the palaeontological evidence, 1 examined the 

 more important fossils somewhat carefully at the close of the 

 meeting. I had a perfectly open mind as to the age of the fauna, 

 for a couple of visits to North Devon and West Somerset had given 

 me the impression that pre-Devonian beds might be hidden in the 

 eastern part of the area. As a paper recently read to the Geological 

 Society of Cornwall assumes the Silurian age of the Morte Slates 

 to be so well established that it may be accepted as the basis for 

 future work, I have been led to re-examine the evidence by a 

 comparison of Dr. Hicks' descriptions and Mr. Michael's figures of 

 the fossils and my notes about them. 



The palgeontological section of Dr. Hicks' paper enumerates eight 

 species, while another name is added in the explanation of the plates. 

 Of the nine species four are described as new, and five are identified 

 as Silurian species ; but in three cases the identification is queried, 

 leaving only two species certainly claimed as Silurian. 



The evidence of six of the nine species does not seem to me to be 

 worth much. Two of the new species belong to genera having so 

 wide a range as Lingula and Spirifera, and thus their evidence as to 

 the age of the rock in which they occur is not very weighty. The 

 occurrence of Cardiola interrnpta, Sow., in the Morte Slates rests 

 apparently on a few shell fragments, which unquestionably came 

 from some bivalved animal, and probably from a lamellibranch. 

 But the ornamentation shown in the specimen figured (Hicks, op. 

 cit., pi. xi, fig. 19) agrees so closely with that of some Devonian 

 species of Fteriiwpecten and Aviculopecten, that the material is 

 quite insufficient to determine the family to which the fragments 

 belong. In the case of the specimens figured as Bhynchonella Leivisi ?, 

 Sow., RhyncJwnella Stricklandi?, Sow., and Orthis rustica, Sow., the 

 specimens figured have a resemblance to the species named ; but they 

 are also very similar to Devonian species, and Dr. Hicks' queries after 

 the names of the two first show that no great stress can be laid 

 upon them. The identification of Orthis rustica is apparently based 

 on the ornamentation ; but the plan of ribbing quoted as " one of 

 the chief chai'acteristics of Orthis rustica " occurs also in the 

 Devonian Orthis interlineata and in other species. 



