148 REPTILIA class m 



about the sixth caudal, and single-headed ribs borne by all the vertebrae as 

 far as the seventh caudal. Abdominal ribs represented by numerous small 

 oat-shaped scutes. Premaxillae small, with three or four recurved teeth. 

 Inferior border of orbit formed by jugal alone. Digits clawed. Habits 

 probably aquatic, as indicated by the comparatively unossified extremities of 

 limb bones. Lower Permian (Rothliegendes) ; Niederbasslich, near Bonn. 



Kaclaliosaurus, Credner. A land form accompanying the preceding ; limb 

 bones completely ossified proximally and clistally, with spongy interior. 

 Extremities much longer than in Palaeohatteria ; humerus and femur of equal 

 length, but metacarpals shorter than metatarsals. 



Proterosaurus, v. Meyer. Attaining a length of 1/5 m. Vertebral centra 

 completely ossified, and united with their neural arches by suture. Inter- 

 centra occur only between the cervical vertebrae, which are elongate, and bear 

 slender ribs. Skull tapering anteriorly, its structure not clearly shown. 

 Hind limb considerably longer than the fore, and distal tarsals less than five 

 in number. Upper Permian (Kupferschiefer) of Thuringia and Hesse, and 

 Magnesian Limestone of Durham, England. P. speneri, v. Meyer ; P. UncJci, 

 Seeley. 



Aphelosaurus, Gervais ; Haptodus, Gaudry. Lower Permian ; Autun and 

 Lodeve, France. Telerpeton, Mantell. Supposed Trias of Elgin, Scotland. 



Sub-Order 2. PELYCOSAUEIA. Cope. 1 



Anterior teeth enlarged, incisor- and canine -like, the remainder conical and 

 molariform ; none of the teeth with lateral cusps, but sometimes serrated. Neural 

 spines enormously developed in some genera. Sacrum of three vertebrae. Limbs 

 very short and strong. 



Family 1. Clepsydropidae. Cope. 



Skull long and narrow, truncated posteriorly . External nares separated, terminal, t 

 opening directly into the mouth. Orbits large, round, placed behind the middle of the 

 si- nil ; supratemporal vacuity small. Quadrate small, nearly enclosed by surrounding 

 bones. Anterior incisors and canines of upper jaw much larger than other teeth. 

 Numerous small conical teeth present on palatines, pterygoids, and vomer. Proximal 

 tarsals two in number. Permian. 



Clepsydrops, Cope. Neural spines of the lumbar and sacral regions greatly 

 elevated. Intercentra present between the dorsal and caudal vertebrae ; 

 anterior ribs double-headed, posterior single-headed. Teeth large, with sharp 

 cutting edges. Permian ; Texas, Illinois, and Kansas. 



Dimetrodon, Cope. Larger than the preceding, skull upwards of 0"5 m. 

 long, and with similar dentition. Intercentra present between the dorsals ; 

 all the ribs double-headed from the axis on. Neural spines rising from the 

 axis until in the dorsal region they are many times longer than the diameters 

 of the centra. Permian ; Texas. 



1 Literature : 



Baur, G., and Case, E. C, On the morphology of the skull of the Pelycosauria and the origin of 

 the Mammals (Anat. Anz. vol. XIII. p. 109), 1897. — The history of the Pelycosauria, with a 

 description of the genus Dimetrodon (Trans. Amer. Phil. Soc. vol. XX. pt. 1), 1899.— Case, E. C, 

 The Vertebrates from the Permian Bonebed of Illinois (Journ. Geol. vol. VIII. p. 698), 1900. 



