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230 well, and is still used often in that original sense or with the exclusion of the Cotylosauria.

There is greater diversity among the Theromorpha as thus distinguished than among the Cotylosauria, the only constant differences from which are the perforated temporal roof, the longer neck, and usually longer legs. Doubtless they were more active and agile animals, and their adaptive radiation was greater. But the primitive characters were less constant. The intertemporal bone is never



present; the interparietals, tabulars, and supratemporals are always smaller; some may be wanting, and the two former are always confined to the occipital surface when present. The quadratojugal is smaller; the lacrimal seldom extends to the nares. The teeth are often wanting on the prevomers; the postsplenial is never present in the mandible though there is a possibility of an additional coronoid, the posterior one of which is always present. The humerus has an ectepicondylar foramen only in the Edaphosauridae; the entepicondylar foramen is always present. The plate-like pelvis never has a large pubo-ischiatic or a true thyroid foramen. There are two or three sacral vertebrae. The fifth tarsale is rarely unossified. No dermal bones have been discovered in any member of the order, and parasternal ribs are known only in the Poliosauridae and