Arduino Mega with SD Wifi Shield Initialization Error

Hi,

I am currently trying to write and read off a microSD card with Arduino Mega 2560 and a Adafruit CC3000 Wifi Shield. The shield was set up according to the Adafruit hookup guide, however no additional wirings were attached to the Mega.

I am using the code below, and have tried many other similar codes and cannot get the SD card to initialize (initialization failed appears in Serial Monitor). I am not sure if I have to connect something to pin 53 on the mega even though the SD card is routed through pin 4? I have attached a picture of the WIFIshield and Arduino for reference.

*/
#define SD_CS_PIN SS
#include <SPI.h>
//#include <SD.h>
#include <SdFat.h>
SdFat SD;

File myFile;
const int chipSelect = 4;
void setup()
{
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }


  Serial.print("Initializing SD card...");
  // On the Ethernet Shield, CS is pin 4. It's set as an output by default.
  // Note that even if it's not used as the CS pin, the hardware SS pin
  // (10 on most Arduino boards, 53 on the Mega) must be left as an output
  // or the SD library functions will not work.
pinMode(10,OUTPUT); // pin 10 must be left as an OUTPUT so it can be set HIGH
 digitalWrite(10,HIGH); // pin 10 needs to be put HIGH to explicitly deselect the WiFi HDG104 chip[code]

  if (!SD.begin(SD_CS_PIN)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  myFile = SD.open("test.txt", FILE_WRITE);

  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to test.txt...");
    myFile.println("testing 1, 2, 3.");
    // close the file:
    myFile.close();
    Serial.println("done.");
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }

  // re-open the file for reading:
  myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("test.txt:");

    // read from the file until there's nothing else in it:
    while (myFile.available()) {
      Serial.write(myFile.read());
    }
    // close the file:
    myFile.close();
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}

void loop()
{
  // nothing happens after setup
}