306 Canadian Record of Science. 



formation. Fortunately, the occurrence of a similar form 

 in the Chazy of Hog's Back had been previously ascer- 

 tained so that this fact, coupled with the one that the 

 almost perfectly horizontal strata on the Quebec side of the 

 Ottawa, were truly Chazy, and characterised by the pre- 

 valence of such types as Orthis imperator (Billings), and a 

 Rhynchonella not distinguishable from the R. plena of Hall 

 — which measures extended across the river to the Ontario 

 side, beneath the waters of the lake and rapids, without a 

 fault or dislocation in well-nigh horizontal beds — make it 

 beyond doubt that these rocks at Britannia are truly Chazy. 

 From these two instances, it follows that the occurrence 

 of Scolithus remains does not necessarily indicate the exist- 

 ence of Potsdam rocks, but that the beds may possibly be 

 newer or higher up in the series. These cases also indicate 

 the necessity of obtaining collateral evidence of every 

 nature, whether paleeontological or stratigraphical, in order 

 to ascertain with any degree of accuracy the precise geo- 

 logical horizon of strata. 



The Ehythm and Innervation of the Heart of 

 the Sea-Turtle.^ 



By T. Wesley Mills, MA., M.D., L.R.C.P.,"Eng. 



Professor of Physiology, M'Gill University, Montreal. 



The present paper is intended in part as a continuation 

 of a shorter one which appeared in Nos. 4, 5, 6, of vol. v. 

 of the Journal of Physiology on the same subject; but more 

 especially asa continuation of my work on Chelonian heart 

 physiology in general. So far as I know there does not 

 exist in physiology a systematic comparison of the resem- 

 blances and differences of any one family or genus. I pro- 

 pose therefore to do for the Chelonians in physiology, to 

 some extent at least, what has been done for them in mor- 

 phology. 



It has hitherto been believed that animals resembling 



* This paper has also very recently appeared in the Jour, of 

 Anat. and Phys., Edinburgh. 



