diff --git a/skimage/transform/_geometric.py b/skimage/transform/_geometric.py
index c006bcbb..71516faa 100644
--- a/skimage/transform/_geometric.py
+++ b/skimage/transform/_geometric.py
@@ -344,7 +344,7 @@ class ProjectiveTransform(GeometricTransform):
 
 class AffineTransform(ProjectiveTransform):
 
-    """2D affine transformation of the form::
+    """2D affine transformation of the form:
 
         X = a0*x + a1*y + a2 =
           = sx*x*cos(rotation) - sy*y*sin(rotation + shear) + a2
@@ -570,7 +570,7 @@ class PiecewiseAffineTransform(GeometricTransform):
 
 
 class SimilarityTransform(ProjectiveTransform):
-    """2D similarity transformation of the form::
+    """2D similarity transformation of the form:
 
         X = a0 * x - b0 * y + a1 =
           = m * x * cos(rotation) - m * y * sin(rotation) + a1
@@ -740,7 +740,7 @@ class SimilarityTransform(ProjectiveTransform):
 
 
 class PolynomialTransform(GeometricTransform):
-    """2D transformation of the form::
+    """2D transformation of the form:
 
         X = sum[j=0:order]( sum[i=0:j]( a_ji * x**(j - i) * y**i ))
         Y = sum[j=0:order]( sum[i=0:j]( b_ji * x**(j - i) * y**i ))