Kyphosis (angular curvature of the vertebral column) or the hump-backed condition in American softshell turtles has been summarized by Nixon and Smith (1949:28). Cahn (1937:185, pl. 25e) illustrated the condition in an individual of _T. spinifer_, and H. M. Smith (1947:119) mentioned kyphotic softshells representing the species _spinifer_ (subspecies _hartwegi_ and _emoryi_) and _muticus_. Neill (1951:10) mentioned two kyphotic _T. s. asper_ and Nixon and Smith (_loc. cit._) recorded the report of a kyphotic _T. ferox_. I have noted the condition in four _muticus_ (subspecies _muticus_, KU 1959-60, 23230; INHS 2148) and seven _spinifer_ (CNHM 22925; subspecies _hartwegi_, USNM 55689; subspecies _spinifer_, UMMZ 52948, 95615; subspecies _emoryi_, KU 2219, 33523, TU 16240). The smallest kyphotic specimen, a hatchling, TU 16240, has a plastral length of 3.5 centimeters. Kyphosis is to be expected in all kinds of softshells as are other abnormalities, such as albinism (reported for _Lissemys_ by D'Abreu, 1928, and partial albinism noted in _T. cartilagineus_ by Mohr, 1929) or congenital absence of limbs (reported by Dutta, 1931, as occurring in the genera _Trionyx_ and _Lissemys_). The cause of kyphosis is not known. Smith (_op. cit._:120) suggested an abnormally early fusion of the costals (= pleurals) with the ribs, and a subsequent differential rate of growth between them and the vertebral column as a hypothesis; Williams (1957:236) proposed that late retraction of the yolk mass, or retraction of an excessively large yolk mass may cause kyphosis. The cause of kyphosis may be of genetic origin or due to some environmental damage to the vertebral column prior to the cessation of growth. The variation in rate of growth of the vertebral column may produce humps of different shapes and sizes. Some of the specimens noted above (UMMZ 52948, 95615) have the carapace only slightly arched and are considered partly kyphotic. There seem to be degrees of kyphosis, a fact that should be taken into account in considering the occurrence of variation in greatest depth of shell. Plastron