Q:

What is the connection between ULN2004 and ULN2804 drivers?

I have an unipolar stepper motor that im driving with an Arduino. As a driver for the motor i bought a ULN2004 driver chip from Ebay. Or so i thought. I might be missing something, but the chip i received has 9 pins on each side, not 8 as my sketch illustrates, and the number on it is ULN2804, not ULN2004.

The link to the data sheet on the ULN2004 listing i bought from spinatronics says it's a ULN2804 chip. I'm unexperienced in how manufacturers set the numbers on the chips. 
Have i bought the wrong chip, or can a ULN2804 driver be used the same way as a ULN2004? 
How do i then change my sketch to implement the last two additional pins of the chip?

A:

Here's the pdf for the ULN2004 chip
It looks like the same application and same specs, set of darlington arrays. ULN2004 has 7 circuits as oppose to ULN2804 which has 8. Both carry 6-15V (CMOS, PMOS compatible inputs), Output currents of 500 mA per driver, and Output Voltage of 50V
It might've been a careless mistake derived from laziness since the chips have the same type of circuitries.
Because these chips are practically the same, you can utilize 2804 the same way as 2004. Only in this circuit, you'd have in8, out8 pins setup the same as in7 and out7

