Authorial simile in Proteus briefly changes the dog on the beach into a different animal: "Suddenly he made off like a bounding hare, ears flung back, chasing the shadow of a lowskimming gull." Then, as he comes back,"trott[ing] on twinkling shanks" like a horse, Stephen's imagination turns the dog into a deer, in the language of heraldry: "On a field tenney a buck, trippant, proper, unattired." Further protean animal metamorphoses ensue, anticipating the kaleidoscopic transformations of the dog in Circe. At the end of the chapter, Stephen himself is captured in the field of animal heraldry: "He turned his face over a shoulder, rere regardant."
The horse-deer-dog stops at the water's edge and sees more life-forms approaching: "At the lacefringe of the tide he halted with stiff forehoofs, seawardpointed ears. His snout lifted barked at the wavenoise, herds of seamorse. They serpented towards his feet, curling, unfurling many crests, every ninth, breaking." "Seamorse," which Gifford identifies as an archaic name for walrus, captures the heaviness of the breaking waves. "Serpented" captures their sinuous many-headed advance. "Every ninth" foregrounds the human habit of looking for patterns in the fluctuations of magnitude in incoming waves.
In the following paragraph, the dog becomes a bear: "The dog yelped running to them, reared up and pawed them, dropping on all fours, again reared up at them with mute bearish fawning." And a wolf: "Unheeded he kept by them as they came towards the drier sand, a rag of wolf's tongue redpanting from his jaws." And a cow: "His speckled body ambled ahead of them and then loped off at a calf's gallop." In the paragraph after that, he plays the part of the fox in Stephen's riddle: "His hindpaws then scattered the sand: then his forepaws dabbled and delved. Something he buried there, his grandmother." And finally he leaves in a flurry of changing forms: "He rooted in the sand, dabbling, delving and stopped to listen to the air, scraped up the sand again with a fury of his claws, soon ceasing, a pard, a panther, got in spousebreach, vulturing the dead."
In the language of heraldry, "passant" refers to an animal walking past the viewer, looking straight ahead. (If he looks at the viewer, the word "gardant" is added.) Unlike other animals, a deer depicted in this posture is called "trippant." Stephen sees his animal "On a field tenney" (tenné = orange or tawny, i.e. the beach), "proper" (in his natural colors, i.e. not changed by demands of iconography), and "unattired" (without antlers, i.e. a dog). When he imagines himself in heraldic terms as "rere regardant," he is thinking of an animal presented looking back over its shoulder. In James Joyce and Heraldry (SUNY Press, 1986), Michael J. O'Shea notes that "None of the English sources to which I have referred uses the expression 'rere regardant' (they simply use 'regardant' to describe the lion looking back over its shoulder) except Barron. But Barron is citing old French usage" (181).
Thornton traces the leopard and panther to several works in the medieval tradition of fantastic bestiaries. The most relevant seems to be the encyclopedic compendium called De Proprietatibus rerum (On the Properties of Things), written in the 13th century by a Franciscan friar named Bartholomeus Anglicus (Bartholomew the Englishman) and translated into English in the late 14th century by a Cornish writer named John de Trevisa. The OED quotes this sentence from the work: "Leopardus is a cruel beeste and is gendered in spowsebreche [i.e., adultery] of a parde and of a lionas." On the other hand, the "fury of his claws" may justify William Schutte's suggestion that Joyce is following Brunetto Latini's Il Tesoro, which explains why the female panther gives birth only once: her young will not wait for the proper time and tear their way out of her womb.