186 REPTILIA. 



vertebrae is 6 in the neck, 20 in the trunk, 3 or 4 in the sacrum (not 

 fused together), and 50 in the tail. The largest element in the pectoral 

 arch is the interclavicle, which exhibits a rhombic expansion at its an- 

 terior end; the clavicles are small and bent; the coracoids, without 

 foramen, have an imperfectly ossified aspect. There is an entepicon- 

 dylar foramen at the expanded distal end of the humerus. In the pelvic 

 arch, the pubis and ischium are thin and laminar, the former with an 

 obturator notch ; the ilium is more robust and considerably expanded 

 at its upper end. A calcaneum (fibulare), an astragalus (tibiale), and five 

 separate distal elements are observed in the tarsus. All the digits, both of 

 the fore and hind feet, must have borne a claw. The hinder is a little 

 longer than the fore limb. The representatives of the abdominal ribs 

 are small and relatively numerous oat-shaped scutes, apparently with- 

 out any keeled or sharply bent median element. The typical and only 

 known species, Palceohatteria longicaudata, occurs in the Lower Permian 

 (Middle Rothliegendes) near Dresden, and attains a length of about 

 0-45 m. 



Proterosaurus is a larger reptile from the Upper Permian 

 (Kupferschiefer) of Thuringia, with completely ossified vertebral 

 centra and with limb-bones comparatively well-ossified at the 

 extremities. Wedge-shaped intercentra (hypocentra) occur only 

 between the vertebrae of the neck. The skull and limb-girdles 

 are too imperfectly known for description. The bones in the 

 distal row of the tarsus appear to be less than five in number. 



The so-called PELYCOSAURIA, as yet only known by fragment- 

 ary specimens, seem to be early Rhynchocephalians allied to 

 the genera just mentioned. They are known chiefly from the 

 Permian of Texas, U.S.A., but have also been found in the 

 Lower Permian of Bohemia and perhaps of France. They are 

 described under the generic names of Clepsy drops, Dimetrodon, 

 Naosaurus, etc., and are remarkable for the enormous develop- 

 ment of the neural spines of the dorsal vertebrae, which some- 

 times bear branches (fig. 115). The quadrate bone, so far as 

 known, is rather small and completely enclosed in the surround- 

 ing elements. 



Sub-Order 2. Rhynchocephalia Vera. 



The typical Rhynchocephalia seem to have attained their 

 maximum specialization and widest geographical distribution in 

 the latter part of the Triassic period. Some European Jurassic 



