52 Proceedings of the Royal Physical Society. 



question still open to discussion. The species appear to be 

 distinct from any yet described from British rocks. I am 

 indebted to the kindness of Mr Brown and Mr Henderson, for 

 the loan of the specimens exhibited. 



IV. Mr John Gibson exhibited specimens of the Colorado 

 or potato beetle {Doryphora decemlhuata), from Ontario, 

 Canada. 



V. Professor Duns exhibited two heads of roe deer (Cervus 



capreolus), whose horns present striking divergences from the 



normal form. One of them, killed at Airds, Argyleshire, has 



the left beam shaped like a highly-developed second year's 



" pricket," while the right resembles the regular antler of the 



third year. At the root of the left a second beam or " pricket" 



has sprung up a little behind the large one ; and another, more 



to the front, rises at the side of the right beam. But these 



are not mere tynes. They have an independent place on the 



frontals, and possess well-developed "burrs." The chief 



"burrs" are unusually large — one of them even partially 



shading the eye. In the second the horns, instead of rising 



perpendicularly from the head, are divergent, like those of 



the fallow deer (Gervus dama) and the red deer {Cervus 



elaphus). Some remarks were made by Professor Duns on 



the physiological explanation of such abnormal forms of 



horns among the Cervidce. The normal conditions of growth 



were contrasted with the highly marked variations in the 



specimens exhibited. The horns of the roe spring at once 



upward from the frontals. They have no curved forward 



direction, as in the Airds specimen, and no lateral divergence, 



as in the other. The fawn is hornless during the first year ; 



in the second, simple stems, or "prickets," appear; in the 



third, the first tyne is formed extending to the front; the 



fourth is marked by the growth of another tyne standing to 



the back. The antlers are not fully developed till the sixth 



year. 



