"Canis Major is dominated by the star Sirius, popularly called the Dog Star, the most brilliant star in the entire sky; almost certainly the constellation originated with this star alone. Aratus referred to Canis Major as the guard-dog of Orion, following on the heels of its master and standing on its hind legs with Sirius carried in its jaws. Manilius called it 'the dog with the blazing face' ...

Classical Greek descriptions ... placed Sirius in the dog’s jaws. Even though the name Sirius was known to Hesiod, Ptolemy in the Almagest called it simply ‘the Dog’, describing it as 'the star in the mouth' ..."

The horizontal wooden beam in the mouth of Sun could represent summer solstice, and Ptolemy's 'star in the mouth' could refer to the 'mouth of the River', Eridu, i.e. to Canopus.

... The city of Eridu was the southernmost of 32 Sumerian cities. The sacred geography of Sumer - if such a concept existed - ought to have put an Eridu constellation just before summer solstice (beyond which Sun had to return because of the 'sea' in front) ...

When a celestial 'person' reaches the horizon in the west it disappears from view, as if it was swallowed. Already from noon however is the descent beginning. Standing in the middle of the day east is in one direction and west in the opposite. From the horizon in the east there is a gradual increase in height up to zenith, then the decrease is beginning.

It is like when a function increases up to a point of maximum and there changes its derivative sign from + to -.

The happy Sun face at the stern of Argo Navis could indicate the horizon in the west is still far away. Sirius is a sign of light also beyond midsummer.

Although for a dog the mouth is next station beyond his nose. Sirius is heading towards the Mouth (of the River, Canopus) with 12 minutes per year.