The first toe in males of _T. ornata_ is uniquely widened, thickened, and inturned. Males of some other species of _Terrapene_ have greatly enlarged rear claws, some of which turn slightly inward, but none has the flexed first toe hooklike as it is in _ornata_ (a modified first toe, resembling that described for _T. ornata_, has been observed in a live male of _T. klauberi_ [now KU 51430] since the preparation of this manuscript). In males of _T. ornata_ the penultimate phalanx of the first toe has a normal, vertical articular surface on its proximal end. However, the distal articular surface (when viewed from the distal end of the phalanx) has its axis rotated away from the vertical plane approximately 45 degrees in a counterclockwise direction. As the foot is pronated and extended, and as the digits are flexed, there is a concomitant inward rotation of the first metatarsal at its proximal joint; this rotation, combined with the divergent planes of the articulating surfaces on the penultimate phalanx, cause the ungual phalanx to be flexed at right angles to the inner side of foot, in a plane perpendicular to that of the other toes (Fig. 21). The precise function of the modified first toe of males is unknown, although it is reasonably safe to assume that the modification is closely associated with clasping during coition. In the matings that I observed, the inturned first claw of the male secured a hold on the female's rump or just beneath her legs, whereas the remaining three toes gripped the edge of her plastron. The combined hold, on shell and skin, clearly affords the male a more secure position during coitus (whether the female clasps his legs with hers or not) than would a hold on skin or shell alone. Possibly intromission can be maintained in this position even when the female is attempting to escape. In males the plastron is less concave in _T. ornata_ than in _T. carolina_. Furthermore, males of _T. ornata_ are, on the average, smaller than females, whereas the reverse is true in _T. carolina_. Possibly the ability of the male to secure an especially firm grip on the female enhances the probability of small males mounting and inseminating larger females, whereas successful matings might otherwise be limited to pairs in which the male was the larger member. It is worthy of note that turtles of the genus _Terrapene_ are seemingly the only North American emyids that carry out the entire process of mating on land; other, semiterrestrial emyids (for example, _Clemmys insculpta_ and _Emydoidea blandingi_) return to water for actual coition, although the precoital behavior sometimes occurs on land.