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Show 1904.] IN LIZAKDS OF THE GENUS TILIQUA. 157 11u cth®. British Museum,' Mr. Boulenger uses as part of his definition of the Scincidae*the sentence " Ossified abdominal ribs are absent ^; and in defining the Anelytropidfe f he includes in that definition the phrase " Abdominal' ribs present." It is not absolutely clear from the wording used whether these two nearly related families are to be distinguished (inter alia) by the absence 01 piesence of abdominal ribs ' (i. e., as already pointed out, the vential moieties of post-sternal ribs) or by the mere absence or piesence of ossification in such ribs. In any case, not only has Peters figured complete hoops in Acontias, but I have been able Ventral flap of musculature (B ) in which lie the abdominal ribs, turned down to • show the deeper-lying muscles (C), in which are imbedded the true ribs (D). to show in the present communication that considerable vestiges of the ventral moieties of post-sternal ribs occur in Tiliqua. It is to my mind possibly a matter for further enquiry as to how far the median ventral region of the post-sternal ribs which actually meet each other behind the sternum may not be actually a parasternum fused with true ribs. For the median region of the chevrons, whether of undoubted abdominal ribs or of true vertebral ribs, appears at the surface of the abdominal musculature. This median region, therefore, at least of the post-sternal true ribs may conceivably be a vestige of a parasternum in those Text-fig. 30. Lacertilia where such ribs occur. * Vol. iii. p. 130. f Vol. iii. p. 430. |
