Let us see what we can do ...

What we have for the 341 BC listing is:

*hippeis de kai harmata kai sunōridas ouk elattous tōn muriōn*

My reading of this is:

cavalry (*hippeis*) and (*de kai*) chariots (*harmata*) and (*kai*) two-horse teams (*sunōridas*, which could just mean 'team' generally but usually signifies a pair) not less than (*ouk elattous*) ten thousand (*tōn muriōn*, literally 'a myriad')

This I would interpret as the cavalry plus the chariots equals at least ten thousand in total, but whether this is the total number of horses or of cavalry plus chariots plus horse teams (which could add up to the same amount) is unclear.

I think you would be justified in interpreting this as either:

1) More chariots than usual, or

2) More cavalry than usual.

In effect, Diodorus has the Carthaginian army consisting of 70,000 infantry and not less than 10,000 mounted troops.

Going back to XVI.67, we have:

*harmata de triakosia, sunōridas de huper tas diskhilias*

which we can recognise as 300 chariots, more than 2,000 '*sunōridas*' - and here the 'sunoridas', which do not match up with the chariots, seem at a loose end and there is no mention of cavalry. Care to guess that Diodorus might have put '*sunōridas*' where he meant '*hippeis*'? That would give 300 chariots and 2,000 cavalry (or maybe even 4,000 cavalry if he was counting in pairs).

Returning to XVI.77, we come to guesswork time.

My guess is that the Carthaginians would not have undertaken an order of magnitude increase in chariot strength as of 341 BC: the armies for which we have figures fielded chariots in the hundred, and I suspect that in an era where the popularity of the chariot was on the wane Carthage would not undertake sudden mass production and field thousands of them, at least not without a very good reason.

Assuming the number of chariots was along the lines of previous armies, say a maximum of 500 and probably less than that, and allowing two or four horses for each chariot, and assuming Diodorus was counting horses rather than men (not necessarily a tenable assumption), we are left with a likely maximum of 2,000 chariot horses and hence at least 8,000 cavalry, which would be double the number known for any previous Carthaginian army.

I emphasise this is guesswork, but to me a doubling of cavalry numbers seems a more likely proposition than a tenfold increase in the number of chariots between 396 and 341 BC. The problem area is the *sunōridas*, which a) imply two-horse teams whereas received opinion is that the Carthaginians were using four-horse chariots and b) may be wrongly used in the context of the 345 BC expedition, *hippeis* being intended instead. This would give us a probable twofold increase in cavalry numbers as of 341 BC and hence perhaps an indication that Numidians were arriving on horseback - or at least with mounts.

That at least is my conjecture. Of course, it could be that the Carthaginians in 345 BC stocked up on horse teams on the basis that not all of them would survive the crossing, but even so, as you observe, 2,000 pairs for 300 chariots seems a little excessive.

A final thought: Numidians may have taken more than one horse apiece. Could Diodorus' *sunōridas* mean not chariot teams but rather Numidians, each with a pair of horses? This might solve all our problems ...