The Kugel Celestial Globe, an antique silver celestial globe dated to the second or third century A.D., shows Boötes holding two dogs. However the dogs are engraved rather crudely compared to the rest of the constellations so perhaps they were added at a later time. If the Kugel globe canines are for real they would represent the earliest known depiction of Boötes' dogs. Kugel Celestial Globe at the Galerie J. Kugel.
Top Drawing: The Dolphin of the Ancients taken near (symbol) Line, called by our seamen a Porpus.
Bottom Drawing: A Dolphin as it is usually called by our seamen taken in the open sea.
- from "A Voyage to New - Holland, &c. In the Year 1699" by Captain William Dampier.
There is infrequently some confusion between Hevelius' alternative name for this constellation, Tigris, with the name of an obsolete Plancius constellation called Tigris flu (ie. fluvius, meaning river). These two Tigris constellations were totally different and were located in opposite regions of sky.
The word monoceros is from the Greek, monokeros, meaning one horn. This constellation name is often misspelled as Monocerus (note the 'u' instead of an 'o'). If after reading the pdf download you are curious about the Unicorn Tapestries you can find out more about them here.