I am not sure if anyone else has seen the Chinese Wikipedia article for the Saṃyukta Āgama, but it is awesomely detailed. There has been a lot of research into the Saṃyukta Āgama since the early 20th century because there was some discovery of commentaries in the Yogācārabhūmi indicating that this collection was the first group of sūtras to historically appear, and it provided the basis for the other āgamas.
Unfortunately, the most complete Chinese Saṃyukta Āgama (T. 99) had its fascicles (scrolls) in disorder, and its study was been mostly neglected, so this was never noticed and caught. Much worse, two fascicles were lost, and accidentally substituted with two fascicles of a late text about King Asoka! The text stayed messed up like that for around 1500 years.
Then in the early 20th century things started to change a lot. China was full of radicals, and many Buddhists wanted to take drastic measures to modernize and reform Buddhism. There was a lot of interest in the āgamas and other traditions that had been either neglected or mixed up in syncretic interpretations over the centuries. Over time, a few scholars found the correct ordering of the Chinese Saṃyukta Āgama and put it back in proper order. The most important scholar of this task was the scholar-monk Yin Shun.
As the structure of the Saṃyukta Āgama was being investigated, it was also found that the text is divided into three aṅgas and seven vargas. The first aṅga, the sūtra aṅga, is believed by these scholars to be the first historical collection of Buddhist sūtras, containing the earliest core doctrines of Buddhism. As in the Saṁyutta Nikāya, the Saṃyukta Āgama's sūtra aṅga is divided into four vargas that can be aligned with the Four Noble Truths.
- skandha-V: suffering
- ṣaḍāyatana-V: suffering
- nidāna-V: arising & cessation
- mārga-V: the path
From the forward by Roderick S. Bucknell to The Fundamental Teachings of Early Buddhism, by Choong Mun-keat:
Briefly put, Yin Shun’s claim is that the distribution of the sutras into four nikāyas/āgamas did not take place at the First Council; initially the sutras were grouped in a single collection, whose structure is largely preserved in the extant SN and SA. The other three principal nikāyas/āgamas were developed subsequently, probably at the Second Council, in response to a substantial increase in the number and size of the remembered sutras that had taken place during the intervening century. These conclusions are based in large part on a demonstration that the contents of SN/SA fit the first, second, and third categories in the traditional aṅga classification (sūtra, geya, vyākaraṇa), i.e. that SN/SA is structurally archaic. It follows that SN and SA are of special significance both historically and doctrinally — which helps explain why the author of the Yogācārabhūmiśāstra saw fit to include in his great treatise a lengthy commentary on the sutra-aṅga portion of SA.
What follows is a basic outline of just the sūtra aṅga of the Saṃyukta Āgama, along with its corresponding sūtra numbers in the received edition as found in the Taishō Tripiṭaka, CBETA, etc. Note that two fascicles are still missing, and are very unlikely to be found in the future. However, the corresponding Pali saṁyuttas, along with the Chinese commentaries can give us a clear idea of what the missing materials contained.
The abbreviation “-V” indicates varga, “[…]” indicates missing material, while the abbreviation “f.” is shorthand for “fascicles.” The number of fascicles is given to convey to the reader the approximate amount of material in each varga. In total, the sūtra aṅga contains 26 fascicles and around 665 sūtras. The Saṃyukta Āgama is supposed to be 50 fascicles, but only 48 fascicles are extant.
sūtra
skandha-V, 5 f.
skandha 陰
1-32
256-272
59-87
33-58
103-110
ṣaḍāyatana-V, 5 f.
ṣaḍāyatana 六入處
188-255
1164-1177
273-282
304-342
nidāna-V, 9 f.
nidāna 因緣
283-303
343-370
āhāra 食
371-378
satya 諦
379-443
dhātu 界
444-465
vedana 受
466-489
mārga-V, 7 f.
smṛtyupasthāna 念處
605-639 [...]
samyakprahāṇa 正勤
[...]
ṛddhipāda 如意足
[...]
indriya 根
[...] 642-660
bala 力
661-703
bodhyaṅga 覺支
704-747
mārga 聖道分
748-800
ānapānasmṛti 安那般那念
801-815
śikṣā 學
816-832
avetyaprasāda 不壞淨
833-860
If anyone has corrections or other info, by all means post away.