188 Correspondence — Dr. G. Linnarsson. 



true, but not the former. Let us test the case by that of the North 

 Suffolk Cliff, which from Kessingland to Yarmouth, a distance of 

 fifteen miles, forms the natural section of a tract of country of similar 

 structure which extends inland for nearly forty miles ; and over 

 which tract, whenever pits show the junction of the sand with the 

 clay, they disclose exactly the same features attending it as the cliff 

 does. Now this cliff, except where the valley denudation interrupts 

 it, is formed by a continuous deposit of undisturbed horizontally 

 bedded sand, containing marine mollusca and other marine organ- 

 isms, overlain nearly throughout by the morainic clay, often twenty, 

 and averaging fully twelve feet in thickness, the junction of the two 

 being absolutely undisturbed except in one or two places where, for 

 a space of a very few yards only, the clay slightly dents into and 

 disturbs the top of the sand, showing as it appears to. me places 

 where floes grounded ; and the only departure from this in the 

 district inland is that bosses of the contorted Drift occasionally 

 protrude there through the sands. Now I say that it is a physical 

 impossibility that the whole of this thick sheet of morainic clay, 

 fifteen miles wide by forty long, can have been dragged for forty 

 miles over the sand without either crumpling or destroying it in the 

 least, and without incorporating part of such sand and of the contorted 

 Drift bosses into itself. This impossibility becomes more striking 

 if we supplement the weight of this sheet of clay by the many-fold 

 greater weight of the ice which Mr. Geikie contends overlaid and 

 dragged it, "gradually diminishing" though that ice may have been 

 from the prodigious thickness usually appealed to by Mr. Geikie. 



I hope that in the above I have made the distinction between 

 our views clear ; and I venture to think that Mr. Geikie, with his 

 numerous interglacial periods, his exaggerated ice-sheets, and his 

 assumption of the truth of Dr. Croll's theory, is hardly the person 

 who should chai'ge those who differ from him with " preconceived 

 ideas " in glacial geology. S. V. Wood, jun. 



FEBRUAJiY 16, 1878. 



ON THE TEILOBITES OF THE SHINETON SHALES. 



SiK, — Among the fossils described in Mr. Callaway's interesting 

 paper on the Upper Cambrian Eocks in South Shropshire (Quart. 

 Journ. Geol. Soc, vol. xxxiii. p. 652 seqq.), there are some Trilo- 

 bites of whose relations to forms previously known I might venture 

 a few suggestions. 



I do not think that Conocoryphe monile is very nearly related to 

 such species as C. striata. By the stronglj^-lobed glabella and the 

 dotted marginal furrow, it approaches to Angelin's Euloma, a genus 

 characteristic of the Swedish Ceratopxjge Limestone, which occupies 

 about the same position as the English Upper Tremadoc. The fauna 

 of the Ceratopyge Limestone is decidedly Lower Silurian, but also 

 the Tremadoc group — at least the Upper — has to me always seemed 

 to be, palseontologically, more related to the Silurian than to the 

 Cambrian. The Lower Graptolite Schists immediately overlying the 



