President'' s Address. 15 



Five species of Cephalopoda are present in the Durness 

 limestone, and amongst them we again observe a strong 

 similarity to American forms. In fact, out of the five, three 

 are provisionally referred to American sj)ecies, whilst the 

 fourth has a strong resemblance to another. Besides these 

 shells Salter was able to determine what he believed to be a 

 new genus, Filoceras, a broad, conical, and slightly curved 

 shell. The siphuncle and septa are combined in one, as a 

 series of conical curved partitions, which fit into each other 

 sheathwise. Salter considered this to be the simplest type of 

 Cephalopod shell known. The genus is clearly allied to the 

 American forms called Endoccras, in which the siphuncle is 

 very large, with a pointed termination. 



The full list of Durness Cephalopoda comprises — 



Ortlioceras mendax, Salter (near 0. multicameratum, 

 Hall, of the Trenton Group =Llandeilo). 



Ortlioceras arcuoliraticm, Hall, Do. 



„ vertehrcde, „ Do. 



„ undulostriaticm „ Do. 



PiJoceras invaginatum, Salter. 



The analogy of the Durness fossils with American forms 

 is not only that of identity of species, but even in lithological 

 character and general appearance. Many of the fossils 

 derived from this " hard, marbled and veined grey limestone " 

 are filled with siliceous matter, and their mode of weatherino- 

 quite bears out the analogy instituted by IMurchison between 

 them and specimens sent from kindred strata in Canada by 

 the late Sir W. Logan.* 



In concluding his remarks on the American facies of the 

 Durness fossils Salter observed, ''there are, i\\m,five identical, 

 three doubtful, four which may fairly be called representa- 

 tive forms (the Machcrea, the Ortlioceras, MurcMsonia angido- 

 cincta, and Pleurotomaria), and Piloceras is a new genus 

 found in Canada and in Scotland." " That this truly ]^orth 

 American assemblage should be found in the extreme north 

 of Scotland, on the same parallel as the Canadian — that 

 species of Machirca and Rapliistoma, resembling those of the 

 "" Quart. Jour. Geol. Soc, xv., p. 369. 



