Crawford is misleading in his type description of 428/1 when he says the jug and lituus are connected to the consulship like the eagle. The eagle is better read as imperium, specifically imperium deriving from the Roman people. Broughton believes Cassius was himself an Augur and I tend to agree. (Cic. Att. 9.9.3) The letter well illustrated the power and importance of the position and close connection between religion and constitutional law.
It is of great importance to Caesar that there should not be an interregnum: and that he secures, if the consuls are “created” by the praetor. However, it is on record in our augural books that, so far from consuls being legally capable of being created by a praetor, the praetors themselves cannot be so created, and that there is no precedent for it: that it is illegal in case of the consuls, because it is not legal for the greater imperium to be proposed to the people by the less; in case of the praetors, because their names are submitted to the people as colleagues of the consuls, to whom belongs the greater imperium. Before long he will be demanding that my vote in the college should be given, and he won’t be content with Galba, Scaevola, Cassius, and Antonius…
Liv Mariah Yarrow 