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The Ottawa Naturalist 



[April 



position. Both consider the Hme to have been 

 precipitated from solution by various agents. The 

 older hypothesis holds that the high percentage of 

 carbon dioxide in spring water is reduced when it 

 enters the lake. As a consequence, the calcium 

 carbonate, which has been held in solution through 

 the presence of the excess carbon dioxide, is pre- 

 cipitated. The other theory attributes the same 

 result to the work of algae which remove the carbon 

 dioxide. It is quite possible that both agencies have 

 been operative at MacKay Lake ; but, however 

 precipitated, the marl in a finely divided state, would 

 be injurious to the molluscan fauna and account for 

 its depauperation. 



Another factor which no doubt must have exerted 

 considerable influence in this connection was the 

 colder climate which probably existed when the 

 marl was accumulating. Such conditions would tend 

 to make short thick shelled forms with the vital 

 organs concentrated as much as possible. A glance 

 over the marl fauna shows this to be conspicuously 

 true. Valvala, Amnicola, the represented species of 

 Planorbis, all belong to this class. Lymnaea galhana 

 with its shouldered thickset whorls is a remarkable 

 contrast to Lymnaea siagnalis appressa. Planorbis 

 trivolvis a large thin shelled species is missing from 

 these marl beds. 



The marl of MacKay Lake, therefore, seems to 

 have a depauperate fauna due to an adverse bot- 

 tom environment and, probably, to a cold climate. 

 It would be interesting to note if, in other districts, 

 similar results could be obtained from a comparative 

 study of the fossil and recent forms. MacKay Lake, 

 however, lends itself particularly well to this kind 

 of study as the marl beds are in such close proximity 

 to the lake. Instructive results would probably be 

 obtained if the fresh water fauna of the Toronto 

 formation were subjected to this type of study. 



Note The writer wishes to gratefully acknow- 

 ledge the valuable assistance and suggestions received 

 from Dr. E. M. Kindle of the Geological Survey 

 of Canada. 



MOST UNUSUAL DEER HEAD WITH 

 EYE TEETH. 



The Division of Exhibits of the United States 

 Food Administration, Washington, offers to assist 

 any museum to develop a special exhibit to illustrate 

 the need of conserving foods. A handbook of 

 "Graphic Exhibits" has been printed. Mimeograph 

 copies of plans for larger exhibits have been pre- 

 pared. Copies have been secured of a series of 13 

 charts, designed and written by Elizabeth C. 

 Watson, under the title, "Why Food Conservation 

 is Necessary." All these are sent to any museum 

 upon request. 



The White-tailed Deer (Odocoileus virginianus), 

 is well known as a bearer of great variations. The 

 horns of the older animals exhibit many freak forms 

 but it is not usual that a natural freak is seen in a 

 young deer. The following note is of a freak in a 

 young deer not over four years old and refers to 

 the teeth and not to antlers, in which there are "eye 

 teeth" or tusks (quite well developed for the age) ; 

 both are evenly matched and slightly curved back, 

 standing out from the jaw about three-eighths of an 

 inch. A characteristic of the deer family is the 

 absence of front teeth in the upper jaw, the only 

 exception being found in the Elk group (Cervus), 

 which when over four years usually develop eye 

 teeth in the male sex only. Taking the formation 

 of teeth in all the larger animals, the majority still 

 carry the eye teeth, or show signs that they did in 

 generations of long ago, and I conclude, therefore, 

 that the deer family also had normal teeth in earlier 

 times so it would be hard to say just how many 

 generations this little deer has been thrown back to 

 his former ancestors. I enquired at the Victoria 

 Memorial Museum, Ottawa, if the officers there 

 had ever known of this freak before and the 

 Director replied that he could find no previous re- 

 cord. I also wrote to the U.S.N.M., Smithsonian 

 Inst., Washington, D.C., and was informed that it 

 is of most unusual occurrence, though they have one 

 from Arizona. I gather, however, that the Arizona 

 record is the only one they know of, but, in this, I 

 may be mistaken. The specimen here recorded was 

 killed near Yahk, B.C., in December 1917, and 

 now forms part of my collection. 



C. Garrett, Cranbrook, B.C. 



As an example of the possibilities of economic 

 zoology, it is interesting to report that the U.S. 

 Biological Survey which has long been engaged in 

 the control of rodent and other pests in various parts 

 of the country, has detailed a staff to France to make 

 similar attempts against the rats that infest the battle- 

 fields. These animals, disgusting in themselves, are 

 also a source of danger to the trenches by their 

 habits of undermining and to the troops owing to the 

 food and material they destroy and their potential 

 possibilities as disease carriers. Should even par- 

 tially effective means of control be evolved they will 

 demonstrate the practical value of scientific research 

 in a most convincing manner. 



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