46 Correspondence — M. Jules Marcou. 



The country explored stretches from the N.E. corner to the S.W. 

 Every locality in wliich lignite had been met with was visited. The 

 most northerly of these, at Husavik, presents a coast-section showing 

 200 feet of tuffs with bands of lignite, 200 feet of the same with 

 marine shells, and an immense series of overlying tuffs, which are 

 untbssiliferous, and were followed, ten miles further north, to Tjornes, 

 almost within the Arctic Circle. The shells, a series of which were 

 exhibited, indicate a warmer sea, and, in the author's opinion, are of 

 an age a little anterior to the Crag. It is hoped that Dr. Gwyn 

 Jeffreys, who has several times examined them, may pronounce a 

 definite opinion in regard to this. A number of sections towards 

 the interior were visited, one of the finest being in a caiion near 

 Hof, where the sides are upwards of 1000 feet high, and nearly 

 vertical, exhibiting an alternation of semicoluranar basalts, ash-beds, 

 and laterites, capped by rhyolites. These rhyolites are very beautiful, 

 and cap the basalts over a wide area, being themselves overlain by 

 other and more irregular streams of basalt and tuffs. The country 

 has been subjected to immense denudation, and is cut up into rolling 

 flat-topped hills such as characterize basaltic regions elsewhere. The 

 horizon from which most, if not all, the fossil plants from Iceland 

 have been obtained, is that of the rhyolites — a more recent series 

 than any represented in the Bi-itish Isles or even in the Faroes. 

 Their age may have been correctly assigned to the Miocene. 



coI^I^:E]s:po:N"^D:B3i^^OE. 



EELATIVE AGES OF AMERICAN AND ENGLISH NEOZOIC SERIES. 



Sir, — Mr. J. Starkie Gardner, in his memoir " On the Relative 

 Ages of the American and the English Cretaceous and Eocene Series " 

 (Geological Magazine, November, 1884, p. 504), says, "Professor 

 Marcou wrote that he considered all the supposed Cretaceous rocks 

 of California to be Tertiary, but without going so far as that, there 

 can be no question about the Tejon Group, at least, being of that 

 age." This statement is erroneous. 



In my "Note sur la Geologic de la Californie " (Bulletin Soc. 

 geol. France, tome xi. p. 407, 1883), which I suppose is the paper 

 referred to, I have described the Cretaceous rocks of the vicinity of 

 Shasta-city as being the only region of California, so far as explora- 

 tions have yet been made, where the Cretaceous rocks truly exist. 

 It is what Mr. Starkie Gardner calls " the Shasta group," " held to 

 be of the antiquity of the Gault." On that age nothing yet definite 

 can be said ; and I believe it is prudent to reserve expressing a 

 decided opinion until more material has been collected and described. 



As to the " Chico group " quoted as the " supposed equivalent to 

 the Chalk formation of Europe," I have shown the palseontogical 

 reasons why it should be considered as representing the lower part 

 of the Eocene. At Chico creek, where it was first discovered, only 

 two or three degenerate Cephalopoda have been found, amid a magni- 

 ficent and very numerous fauna of Gasteropoda and Acephala, 

 characteristic of true Lower Tertiary in America as well as in Europe. 



