88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



present held was apparently indicated by a small terrace which appears a 

 foot or 18 inches above the present level of the water, and the limy deposit 

 was apparently formed at this level as well as at the present one. 



It was noted that the branches of trees and other drift material which had 

 settled to the bottom of the lake were covered by the incrusting algal deposits 

 as far down as twelve or fifteen feet. These fragments may possibly have rolled 

 down the steep slope after the formation of the incrustation, but of this there 

 was no good evidence visible. If deposition as the result of the activities of 

 the algje went on faster near the water surface, as theoretically it should, since 

 here the plants find most favorable light conditions, the peculiar overhanging 

 form of the terraces might easily result. This type of deposit is what should 

 theoretically result from the work of Zonotrichia, if it grew under very favor- 

 able conditions and in great abundance. It is probable, from the color of the 

 broken fragments, that the algae are responsible for the formation of the 

 whole of these deposits, or for most of them. 



Further work on the identity of the Blue-green alga most abundant in the 

 spongy calcareous covering of one of the branches which was collected at the 

 time of my visit to the locality shows that the organism is a cellular Blue-green 

 alga, and not a filamentous one like Zonotrichia. This cellular type develops 

 irregular aggregations of rounded or oval, very small cells, which apparently 

 seldom arrange themselves in strings. The genus or species has not been 

 identified. 



Mr. G. W. W. Barclay, when describing some " Algoid Lake- 

 balls " that he found in Loch Kildonan in the Hebrides,' states that 

 the balls are from a quarter of an inch to 3 or 4 inches in diameter 

 and lie side by side in great numbers. In some cases a complete 

 small ball is found inside a larger one and the balls while usually 

 spherical may be irregular in shape. He found them composed of 

 innumerable algal filaments, so intertwined and matted together as 

 to form an outer covering of an almost felt-like consistency that is 

 about one-twentieth to two-twentieths of an inch in thickness. The 

 interior seems to consist of mud but the microscope shows that 

 they are composed of a filamentous alga {Cladophora glomerata). 

 The decomposed remains of the inner ends of the filaments are 

 mingled with diatoms, but there does not appear to be any calcareous 

 matter present. 



Somewhat similar lake balls have also been found in several other 

 European lakes. 



Mr. A. C. Seward in his " Fossil Plants " ^ writes as follows : 



On the shores of the Great Salt Lake, Utah, there are found numerous small 

 oolitic calcareous bodies thrown up by the waves.^ These are coated with the 



'Proc. Royal Soc, Edinburgh, 1886, Vol. 13. pp. 845-848, pi. XXX. 

 ^ Cambridge Univ., Press, Vol. i, 1898, pp. 122, 123. 



'Rothpletz, A., ijber die Bildung der Oolithe, Bot. Cent., Vol. 51, p. 265, 

 1892. 



