This consciousness turns back; it doesn't go further than name-and-form In SN 12.65, we read about the cyclic relationship between consciousness and name-and-form, which has been asked in this question.

However, this sutta also has the curious phrase in bold below.

What does this phrase mean? "This consciousness turns back; it does not go further than name-and-form."

How does it fit with the rest of sutta?

As translated by Bhikkhu Bodhi:


  “Then, bhikkhus, it occurred to me: ‘When what exists does birth come
  to be?… existence?… clinging?… craving?… feeling?… contact?… the six
  sense bases?… name-and-form? By what is name-and-form conditioned?’
  Then, bhikkhus, through careful attention, there took place in me a
  breakthrough by wisdom: ‘When there is consciousness, name-and-form
  comes to be; name-and-form has consciousness as its condition.’
  
  “Then, bhikkhus, it occurred to me: ‘When what exists does
  consciousness come to be? By what is consciousness conditioned? ’
  Then, bhikkhus, through careful attention, there took place in me a
  breakthrough by wisdom: ‘When there is name-and-form, consciousness
  comes to be; consciousness has name-and-form as its condition.’
  
  “Then, bhikkhus, it occurred to me: ‘This consciousness turns back; it
  does not go further than name-and-form. It is to this extent that one
  may be born and age and die, pass away and be reborn, that is, when
  there is consciousness with name-and-form as its condition, and
  name-and-form with consciousness as its condition. With name-and-form
  as condition, the six sense bases; with the six sense bases as
  condition, contact…. Such is the origin of this whole mass of
  suffering.’


As translated by Bhikkhu Sujato with Pali version included (from here):


  This consciousness turns back from name-and-form, and doesn’t go
  beyond that.
  
  paccudāvattati kho idaṃ viññāṇaṃ nāmarūpamhā na paraṃ gacchati.
In his analysis, Buddha sought to identify the semiotic precursor/counterpart for the experience of death. Going backwards from death, he identified the notion of "life" (jati, the notion of separate organism that gets born and dies) as the precursor/counterpart of death.

Going further backwards, he identified a chain of precursors/counterparts supporting each other in the process of semiotic development. These were appropriating experience aka becoming, object grasping aka goal-setting, obsession aka craving, associating a feeling with object, contact with object, six doors of contact, and namarupa or the labeled objects themselves.

He then tried to identify a precursor or counterpart for namarupa, information about objects and identities. He realized that vijnana or ability to differentiate objects from their background and from each other (the function that gives rise to our basic awareness of the world), is the precursor/counterpart of namarupa.

Naturally, the next step was to try and identify the precursor/counterpart for vijnana (recognition/differentiation). Upon much thinking, Buddha came to conclusion that namarupa itself was the counterpart of vijnana. Indeed, there may be no differentiation of objects without capacity for recognition, and there is no capacity for recognition without notions of objects.

At that moment Buddha realized that the entire chain of phenomena he has been analyzing, including death, is completely included in the realm of objective thinking. In other words, the entire experience of living and dying is a story our object-obsessed mind is telling itself. This realization was a huge breakthrough and a major step in the direction of Enlightenment.

At a later date, Buddha reconsidered this idea that vijnana and namarupa are each other's precursors and instead came up with an alternative chain which had "accumulated tendencies" (samskaras) and "ignorance" as two more links of the chain. This is the version of DO that ended up becoming the classic we know today.

Anyway, the importance of this realization still stands, that all our experienced phenomena are mind-made ("form is emptiness"), and this mind itself is a reflection of interaction of phenomena since beginningless times. In Mahayana we say, phenomena are empty, and mind is empty as well, these two emptinesses are a reflection of each other and yet they manifest as seeming reality ("emptiness is form"). This relationship is an important topic of analytical meditation in Tibetan Mahayana.