Question about array read using protocol 3.0 implementation in C#

Hello:

I'm trying to read an array, using binary format code and my own
implementation of the 3.0 protocol in C#, at this moment i have made
test with arrays of int2 and float4, seems that the server sends a
header of 24 bytes before the data in the buffer, i need to know what
these 24 bytes mean :), i think that:

00-03 -> ??
04-07 -> ??
08-11 -> typelem
12-15 -> ??
16-19 -> ??
20-23 -> typlen

Can anybody tell me what these 24 means or where to see it in the
PostgreSQL documentation

Thanks in advance.

--
Best regards

Carlos Guzmán Álvarez
Vigo-Spain