LSM303C temperature sensor
From the datasheet: 

It's 16 bits, as you can see from 8.38, and 2's complement. 



It's in °C and the radix point is left of the 3rd bit, which  you can tell from 2.2


So 25.0 degrees C is 0x00C8

and -40.0 degrees C is 0xFEC0

Edit: From actual experiment (see comments from OP) the °C temperature is offset so +25 must be added to get the correct temperature. That does not contradict the datasheet but adds an unexpected bias that contradicts assumptions.