In 2014, Dr Irving Finkel published a translation of the Atra-Hasis text extant on the "Simmonds Ark Tablet" in his book, The Ark Before Noah. He proposed that the original Mesopotamian flood vessel was a giant coracle (a round river boat) rather than a cube as in the Epic of Gilgamesh or the rectilinear vessel described in Genesis 6:14–17. Finkel's hypothesis relies heavily on his interpretation of the Akkadian word kippatum ("circle") as defining the final shape of the hull. However, a forensic analysis of the tablet's internal mathematical data—and the technical appendix in his own book—reveals irreconcilable contradictions to the "Round Ark" hypothesis. This paper demonstrates that: (1) The structural beam dimensions ("ribs") provided in the text are mathematically insufficient to satisfy a circular plan under any physical configuration. A flat circular layout fails the text's explicit area requirement (yielding ≈78 sq nindan rather than the required 100), while a curved coracle profile fails the geometric span requirement, as a 10–nindan rib is physically incapable of bridging a 10–nindan width if subjected to curvature; (2) The volume calculations for construction materials reveal a stark contrast between sexagesimal parsimony and irrational complexity: the data yields perfect integers for both rope (4 šār) and bitumen (8 šār) when applied to a square hull, whereas Finkel's circular model produces chaotic, irrational figures; (3) Finkel's reconstruction relies on the anachronistic use of modern π rather than the historical Babylonian value of 3⅜, thus distorting the scribe's original (assumed) geometry; and (4) The internal dimensions utilize the sexagesimal integer "10 nindan" (60 m), creating a 1:1 ratio between the vessel's length, breadth, and rib span. I conclude that the term kippatum refers to the geometric construction method (circumscribing or inscribing a square) rather than the vessel's final shape. Furthermore, a cladistic analysis of the vessels' geometry reveals a precise mathematical phylogeny descending from Noah's Ark. The Rectilinear-AH ark serves as the mathematical "missing link"—preserving an historical 10:1 length-to-height ratio of Genesis while slightly rounding down its footprint to achieve a standard 1 field area. The volume too was also converted to a "sexagesimally holy" figure, which the Gilgamesh epic later inflated tenfold. Finkel's circular interpretation (Finkel-AH) completely severs this hereditary textual chain proving his interpretation is not only structurally unviable, but phylogenetically untenable.