. Bulletin. Science; Natural history; Natural history. 118 BULLETIN SOUTHERN CALIFORNIA ACADEMY OF SCIENCES VOLUME 74. NUMBER TERMINAL ELEMENTS Figure 8. Number of appendage elements and ap- pendage length plotted against the number of ex- ternal terminal elements (scales or phalanges) for eight species of Baclua. Open circles represent fore- limbs: closed circles, hindlimbs. See text for ex- planation. tibia and fibula and tarsal elements) with loss of the tarsal elements in hicolor and peruana. Bachia trisanaJe has a femoral and tibia-fibula ele- ment while bicolor has no hindlimb element or
. Bulletin. Science; Natural history; Natural history. 118 BULLETIN SOUTHERN CALIFORNIA ACADEMY OF SCIENCES VOLUME 74. NUMBER TERMINAL ELEMENTS Figure 8. Number of appendage elements and ap- pendage length plotted against the number of ex- ternal terminal elements (scales or phalanges) for eight species of Baclua. Open circles represent fore- limbs: closed circles, hindlimbs. See text for ex- planation. tibia and fibula and tarsal elements) with loss of the tarsal elements in hicolor and peruana. Bachia trisanaJe has a femoral and tibia-fibula ele- ment while bicolor has no hindlimb element or only a very short femoral element (based on its position). The pelvic girdle articulates with two sacral vertebrae and consists of an ilium oriented ventro- anteriorly, a posteroventrally projecting ischium and an anteroventral projecting pubis. Unlike the pectoral girdle, the pelvic girdle is much reduced including the reduction and/or loss of the ischium and pubis (B. trisanale) as well as reduction in the sacral diapophysis and finally, complete loss of both sacral diapophyses (B. monodactylus). In all specimens examined, a single, dorsally posi- tioned, anteroventrally oriented element was pres- ent, which I believe to be the ilium. The inter- pretation of this element as an ilium is supported by work on other limbless forms and by some embryological evidence (Cope, 1892a; Essex, 1927: Stokely, 1947). A correlation between a reduction in number of skeletal elements and the shortening of the ap- pendage is indicated in figure 8. In both cases, as the number of distal external structures (, Figure 9. Lateral view of the skull and four cervical vertebrae of Bacliia trisanale: line equals 1 mm. toes or terminal scales on a single blunt ap- pendage) or number of internal skeletal elements are reduced, the total length of the appendage is reduced. This may seem obvious at first but it is not necessarily the case as reduction in the tarsal elements and phalanges in the genus
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