In the standard Ugaritic alphabet, the orthography of the Ṯ has more relatively common variants than just about any other letter. Vita’s drawing in Tropper, 19, and Tropper’s, 26, own discussion amply illustrate the point. Ellison, 694-737, discuses and illustrates these variants at great length in his 2002 Harvard dissertation.
Perhaps the most abnormally interesting variant is the oblique wedge surrounded by a complete () or partial () circle. The drawings are from Ellison 703 and 711 respectively. Both Tropper, 15-16, 19, 26, and Ellison, 706 – 722, devote more print to this variant than to any other.
Dietrich and Loretz speculate that this sign might indicate the Hurrian sibilant phoneme š. But Tropper and Ellison point to several cases where it is rather unambiguously intended to be an Ugaritic Ṯ and very likely phonetically ṯ.
Now here is the abnormal part. The usual symbol for the š phoneme in the short cuneiform alphabet is, abnormally, wedgeless. It is rather an inscribed, sometimes irregular, linear circle (, my drawing). Etymologically, Proto-Semitic Θ, ṯ in Ugaritic and Arabic, becomes or coalesces with š in Akkadian, Hebrew, Old Aramaic, Phoenician and the short cuneiform alphabet. So is there a common orthographic tradition behind the long cuneiform alphabet variant with its enclosing circle and the short cuneifrom as well as a likely common phonetic tradition?
Inquiring Abnormal minds want to know.
While the evils of wild speculation may be calling me again, if you really have an abnormal mind, you might want to check out a paleographic chart showing the development of the Greek letter Θ in the context its Northwest Semitic precursors and remember that Proto-Semitic Θ becomes t (importantly to this speculation not ṭ) in later Aramaic.
Tropper, Josef (2000): Ugaritische Grammatik (Alter Orient und Altes Testament, 273; Münster: Ugarit-Verlag)
Dietrich Manfried and Oswald Loretz, “Ein ‘hurritisches’ Zusatzzeichen des Keilalphabets?“ UF, 25, 137-142