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