61'o E. M. KINDLE CANADIAN PLEISTOCENE CONCRETIONS 



of the same concretions Prof. B. K. Emerson remarks that the "initiating 

 cause entirely eludes our observation.'" ^"^ 



The Labrador specimens figured show different species of Pleistocene 

 fossils filling the role of nucleus in various stages of envelopment by the 

 concretions. 



A remarkable egg-shaped concretion from Alberta, of supposed late 

 Cretaceous age, is shown in plate G. figures 10 and 11. in order to illus- 

 trate another kind of nucleus. This specimen, which in shape recalls the 

 fossil Struthwlithus figured by Eastman.^^ was sent to the Canadian 

 Geological Survey by Mr. C. J. Eeach. of Macleod, Alberta, who supposed 

 it to be a fossil egg and reported that it was one of a dozen or more fotmd 

 together. Doctor Wieland, who, at the writer's request, kindly cut the 

 specimen through the longitudinal and transverse axes, found a silicified 

 piece of wood forming the nucleus of this egg-shaped concretion.^- 



Wliile shells in many cases, pebbles in some, and roots in others furnish 

 the initial starting point or nucleus of numerous concretions, many of 

 the Labrador specimens show no visible nucleus. Where no visible 

 nucleus is present, what has been the initial stimulant or determinant in 

 the formation of concretions? The segregation of mineral matter at a 

 particular point, however small the amount, might, in the writer's opin- 

 ion, be expected to serve as the determining factor for the development 

 of a concretion when other favorable conditions were present. The work 

 of Mendel and Bradley^" and of Herdman and Boyce^* has demonstrated 

 the metal-storing activities of marine mollusks with reference to copper 

 and zinc. They found in some cases as much as 15 per cent of zuic in 

 the ash of the liver of a marine gastropod. Barfurth,^^ in his paper on 

 the molluscan liver, pointed out the large calcium and magnesium con- 

 tent of the livers of various gastropods, which varied with the season. 



^Vny soft-bodied marine invertebrate possessing the ability to store in 



^ Benj. K. Emerson : Mon. V. S. Geol. Surv.. 20. ISOS. pp. 711-720. 



'^ C. R. Eastman : On remains of Strii1hioli1hn^ chcrsonensis from northern China. 

 Bull. Mus. Compar. Zool.. Harvard Coll.. vol. xxxii. no. 7, August, 1S9S. 



^ Dr. Wielands view regarding the nature of this ver.v unusual concretion is given in 

 the following extract from a letter to the writer : "I think those Alberta 'duck eggs* 

 may l>e some uncommonly large development of the •Feistmantelia' concretion phe- 

 nomenon. I have long been noticing lesser forms from small and nearly oolitic to larger 

 and flattened pisolite size in more or less imperfectly silicified trunks. It is to my mind 

 a complex concretionary effect of a very varied expression. But lately Berry has given 

 some figures and a most elaborate account of several of these 'Fcistmautelia' groups of 

 considerable size — nearl.v an inch long" (Flora of the Cheyenne sandstone of Kansas. 

 U. S. Geol. Surv. Prof. Paper 120. 1. cf. pi. xlvii, 4. 5. 19221. 



=* L. B. Mendel and H. C. Bradley : Experimental studies on the physiology of the 

 mollusks. Am. Jour. Phys., vol. 14, 1905, pp. 314-31.J. 



** Herdman and Boyce : Report of the Tbompson-Yates laboratories, Liverpool, ii. 1S90. 



*^ Barfurth : Archiv fiir mikroskopische Anatomie, vol. xxii. 1SS2. p. 473. 



