diff --git a/qpms/cytmatrices.pxd b/qpms/cytmatrices.pxd
index 51641d9..183ec29 100644
--- a/qpms/cytmatrices.pxd
+++ b/qpms/cytmatrices.pxd
@@ -14,6 +14,17 @@ cdef class TMatrixInterpolator:
     cdef inline qpms_tmatrix_interpolator_t *rawpointer(self):
         return self.interp
 
+cdef class TMatrixGenerator:
+    cdef qpms_tmatrix_generator_t g
+    cdef object holder
+    cdef inline qpms_tmatrix_generator_t raw(self):
+        return self.g
+    cdef inline qpms_tmatrix_generator_t *rawpointer(self):
+        return &(self.g)
+
+cdef class TMatrixGeneratorTransformed:
+    pass
+
 cdef class CTMatrix: # N.B. there is another type called TMatrix in tmatrices.py!
     cdef readonly np.ndarray m # Numpy array holding the matrix data
     cdef readonly BaseSpec spec # Here we hold the base spec for the correct reference counting; TODO check if it gets copied
diff --git a/qpms/cytmatrices.pyx b/qpms/cytmatrices.pyx
index 29c8d7c..6ca8afc 100644
--- a/qpms/cytmatrices.pyx
+++ b/qpms/cytmatrices.pyx
@@ -231,10 +231,6 @@ cdef class __AxialSymParams:
 
 
 cdef class TMatrixGenerator:
-    cdef qpms_tmatrix_generator_t g
-    cdef object holder
-    cdef qpms_tmatrix_generator_t raw(self):
-        return self.g
     def __init__(self, what):
         if isinstance(what, __MieParams):
             self.holder = what
diff --git a/qpms/qpms_c.pyx b/qpms/qpms_c.pyx
index c78e764..7f27b17 100644
--- a/qpms/qpms_c.pyx
+++ b/qpms/qpms_c.pyx
@@ -315,8 +315,10 @@ cdef class ScatteringSystem:
     Wrapper over the C qpms_scatsys_t structure.
     '''
     cdef list basespecs # Here we keep the references to occuring basespecs
+    cdef list tmgens # here we keep the references to occuring TMatrixGenerators
     #cdef list Tmatrices # Here we keep the references to occuring T-matrices
     cdef qpms_scatsys_t *s
+    cdef qpms_tmatrix_function_t *tmg # this will ultimately contain pointers to stuff in basespecs and tmgens.
 
     def __cinit__(self, particles, FinitePointGroup sym):
         '''TODO doc.
@@ -341,7 +343,7 @@ cdef class ScatteringSystem:
         for tm in tmobjs: # create references to BaseSpec objects
             self.basespecs.append(tm.spec)
         try:
-            orig.tm = <qpms_tmatrix_t **>malloc(orig.tm_count * sizeof(orig.tm[0]))
+            orig.tm = <qpms_ss_derived_tmatrix_t **>malloc(orig.tm_count * sizeof(orig.tm[0]))
             if not orig.tm: raise MemoryError
             orig.p = <qpms_particle_tid_t *>malloc(orig.p_count * sizeof(orig.p[0]))
             if not orig.p: raise MemoryError