The Spheno-mega-coronas are a further  family of locally convex polyhedra with cyclic symmetry. The polyhedra have two n/d faces, and are 5-uniform. Starting from the "square plated n/d face" (see left hand image of a 7/3 Spheno-mega-corona above) and running through to the "triangular plated" n/d face (right hand image) the vertices are:

Type (A): n/d-4-3-3-4, Type (B): 4-3-3-3-3, Type (C): 3-3-3-3, Type (D): 3-3-3-3-3, Type (E): n/d-3-3-3-3-3

The only n-gonal convex member of this family is the Johnson Solid sphenomegacorona or the "Digonal Spheno-mega-corona" with n=2. If n=3 then the resulting Triangular Spheno-mega-corona is clearly not convex.  

Examination shows this family to be locally convex in the range 2 <= n/d < ~2.8. The local convexity is evident on this 7/3 spheno-mega-corona with only one rotation around the symmetry axis.  The following models with only one rotation around the symmetry axis show that n/d=2.666 (8/3) is clearly convex,  n/d=2.75 (11/4) appears to be marginally convex whilst n/d=2.8 (14/5) appears to contain coplanar faces. (Full 14/5).  It must be stressed that the upper convexity limit has to date only been assessed from a visual examination of the VRML models and has not been explicitly determined.

Spheno-mega-coronas with d>1 and n<=12 for 2<n/d<3 are listed below. As with the spheno-prisms, the solids have a number of internal vertices.  The type (B) vertices are not normally visible from the outside of the solid.  
5/2 7/3 8/3 9/4 11/4 11/5 12/5

Retrograde spheno-mega-coronas are also possible: for example this 7/4 spheno-mega-corona


Like the spheno-coronas, there are additional isomorphs to the spheno-mega-coronas, for example the above image is of a 7/3 spheno-mega-corona isomorph.  These have not been classified, but a further 7/3 spheno-mega-corona isomorph is linked here:

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