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262 Protorosaurus in size, slenderness, and proportions. The single-headed ribs are described by Thevenin as articulating intercentrally.

Lower Permian. ? Aphelosaurus Gervais, France.

Upper Permian. Protorosaurus v. Meyer, Germany.

The nares were described by Seeley as immediately in front of the orbits—an error. There may be a small antorbital foramen, but it is doubtful.

. Slender, terrestrial or subaquatic reptiles about two feet in length. Skull with a single temporal opening, the quadrate fixed and the lateral temporal region moderately broad. No postfrontals; postorbitals large. No parietal foramen. Maxillae and dentaries edentulous, with cutting edges. Vertebrae procoelous without intercentra; twenty-three presacrals, two sacrals, and fifty or more caudals. Caudal vertebrae with splitting point (?). Ribs single-headed, articulating with anterior part of centrum. Coracoid with two median emarginations. Interclavicle T-shaped, the clavicles slender. Parasternals numerous, composed of a median unpaired pices and a lateral splint on each side. Pubes and ischia broadly separated by pubo-ischiatic opening, the ischia with a stout posterior tuberosity. An ectepicondylar foramen in humerus. Manus and pes pentedactylate, with primitive phalangeal formula.

Saphaeosaurus, usually called Sauranodon, has long been classed as a representative of a distinct family of the Rhynchocephalia. The skull, as described by both von Meyer and Lortet, has but a single temporal opening on each side, bounded externally by the postorbital and squamosal (tabular?). There is no lower temporal opening. The structure of the temporal region as described is doubtful. In much probability the tabular, squamosal, and quadratojugal are all present. In all its essential characters it is a Lacertilian with a primitively fixed quadrate. The vertebrae, as figured and described by Lortet, are procoelous, perhaps the first known evidence of such in geological history.

Upper Jurassic. Saphaeosaurus v. Meyer (Sauranodon Jourdan), France.

. Very slender, snake-like, aquatic reptiles, with short neck, long body, very long flattened tail, and small pentedactylate legs; attaining a length of nearly five feet. Skull