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"Vertical section through backbone and ribs of Chelonian (I.) and Mammal (II.). N.SP., neural spine; N.SC., neural scute; T., tubercle of rib; C.SC., costal scute over rib (R.); CA., capitulum of rib; T.P., transverse process; CE., centrum; NA., cavity of neural canal. In the Chelonian the tubercle abuts against the flattened neural spine, and the capitulum against the transverse process. In the Mammal, the tubercle articulates with the transverse process and the capitulum with the centrum." -Thomson, 1916

Mammal and Chelonian Backbones

"Vertical section through backbone and ribs of Chelonian (I.) and Mammal (II.). N.SP., neural spine;…