boolean isPrimordialAntiValue(final int foundAt) {
        if (isDataPage()) {
            final int p = foundAt & P_MASK;
            if (p >= KEY_BLOCK_START && p < _keyBlockEnd) {
                int kbData = getInt(p);
                int tail = decodeKeyBlockTail(kbData);
                int tbData = getInt(tail);
                int klength = decodeTailBlockKLength(tbData);
                int size = decodeTailBlockSize(tbData);
                int offset = tail + _tailHeaderSize + klength;
                int valueSize = size - klength - _tailHeaderSize;
                return valueSize == 1 && _bytes[offset] == MVV.TYPE_ANTIVALUE;
            }
        }
        return false;

    }