These younger descendants differ from Goniatites in their evolute inner whorls, their wider external lobe, and their higher median saddle. 

The lenticular, keeled conch form and evolute, coarsely plicate juvenile whorls of Eoprodromites were anticipated by the Pseudarietitinae. 

They evolved in the Devonian, comprising evolute to involute planispirally coiled conchs quite similar to that of the contemporaneous nautiloids. 

The evolute and the involute of an equiangular spiral is an identical equiangular spiral. 

He gives propositions determining the centre of curvature which lead immediately to the Cartesian equation of the evolute. 

The general shell characters are the evolute coiling and the median keel that is always higher than the lateral ones. 

It essentially separates early and later representatives of the species, which tended to develop evolute coiling through geologic time. 

Both the evolute and involute of a cycloid is an identical cycloid. 

Hence a curve has a unique evolute but infinitely many involutes. 

Of course the evolute of an involute of a circle is a circle. 

From a point above the evolute three normals can be drawn to the parabola, while only one normal can be drawn to the parabola from a point below the evolute. 
