Other muscles with several enumerated parts seem to use primus, secundus, tertius, ..., this is, the masculine nominative of ordinal numbers (masculine because musculus is masculine). This is consistent with the answers in your other question.
Examples of such use are:
(the latter two taken from here)
Where is the correct position for the Latin words for left and right for a muscle or bone name and is there a general rule where to position this word?
In modern (English) usage, the Latin for left and right is not commonly used. Nevertheless, I think we can deduce a general rule by (1) looking at early anatomy books and (2) extrapolating from the use of ...
It seems usage of Latin name for muscles many times does not specify the side of the body in Latin. Instead, they use English (or other languages), e.g. "left/right latissimus dorsi" (e.g. left here). However, the Latin for right and left are still used in some cases. Most of the cases I could find (without attempting to provide an exhaustive statistical ...