I9I3-] STEVENSON— FORMATION OF COAL BEDS. 65 



Lochy for the Fishery Board of Scotland. In Ness, the dredge was 

 filled with fine mud containing fragments of peaty matter and pieces 

 of partially decayed wood. Some exnvise of entomostraca were 

 present but no living specimens were observed. The same condition 

 was found in the other lakes where no attempt was made to de- 

 termine the thickness of the deposit. In these lakes, the water is 

 free from mud and is dark brown, owing to dissolved organic matter 

 from peat. The streams descend from the Highlands, but the region 

 is protected from erosion by a cover of peat, so that only very fine 

 silt is brought down. The brown waters pass out to the sea and the 

 dissolved materials are not precipitated in the lakes. 



The presence of vegetable remains along with those of marine 

 animals in many black shales is by no means proof that the water 

 was shallow nor is the association in any sense evidence that the 

 water was deep. The observations by Agassiz^^ have been cited 

 many times in this connection as though they contain the final argu- 

 ment. In reference to dredgings in the Caribbean sea he says, that 

 the contents of some of the trawls would have puzzled a palaeontolo- 

 gist; there were deep water forms of crustaceans, annelids, fishes, 

 echinoderms and sponges, mingled with mango and orange leaves, 

 branches of bamboo, nutmegs and land shells, both animal and vege- 

 table forms being in great profusion; so that it might be difficult to 

 decide whether one were dealing with a land or a marine fauna. 

 Such a trawl from a fossil deposit would naturally be explained as 

 representing a shallow estuary surrounded by forests ; yet the depth 

 may have been 1,500 fathoms. The large quantity of vegetable 

 matter, thus carried out to sea, seems to have a marked effect in 

 increasing locally the number of marine forms. 



Whether or not any palseontologist would have reached the con- 

 clusion suggested for him by Agassiz is scarcely open to dispute; 

 the palaeontologist's answer to the query would be unequivocal and 

 thoroughly emphatic. Commingling of marine and land elements 

 occurs in shallow as well as in deep portions of the Caribbean, with 



"A. Agassiz, "Three Cruises of the Blake," Mem. Miis. Coiiip. ZooL, 

 Vol. XIV., p. 291. 



PROC. AMER. PHIL. SOC. LH. 2o8 E, PRINTED MAY I3, I9I3. 



