Using python 2.7.10, numpy 1.9.2
If I define a structured dtype in the following manner:

>>>my_dtype = np.dtype({ 
    'names':['A', 'B'], 
    'formats':['f4', 'f4'], 
    'offsets'[0, 8], 
    'itemsize':16})

And I then try to create a new dtype from this dtypes descr:

>>>new_dtype = np.dtype(my_dtype.descr)

Then the two dtypes will not have the same itemsize

>>>my_dtype.itemsize
16
>>>new_dtype.itemsize
12

Examining the descr of my_dtype, we see that it is leaving off the 4 void bytes at the end

>>>my_dtype.descr
[('A', '<f4'), ('', '|V4'), ('B', '<f4')]

What should happen instead:

>>>my_dtype.descr
[('A', '<f4'), ('', '|V4'), ('B', '<f4'), ('', '|V4')]

This has relevance for use of structured arrays with IPython.parallel, as this is how structured arrays are reconstructed when serialized and sent to engines in IPython.parallel. A work-around for the user of course is to define some field that marks the end of the structured data, but it seems that this should not be necessary.