The intercentrum of the present form is fully as large as the pleurocentrum. The significance of this has already been mentioned. The body of the centrum is pierced by a large notochordal canal.

Measurements of the Type of Spondylerpeton spinatum Moodie.

mm.
Length of specimen 60
Length of pleurocentrum 11.5
Height of pleurocentrum to base of neurocentrum 20
Length of neurocentrum 33
Width of neurocentrum at base 9
Width across anterior zygapophysis 12
Width across posterior zygapophysis 10
Length of intercentrum 10
Height of intercentrum 10.5
Height of chevron 3
Length of chevron 18
Width of notochordal opening in centrum 5
Height of same 4.5
Height of neural canal 12
Greatest width of neural canal 6

Family ERYOPIDÆ Cope, 1882.

Cope, Am. Nat., XVI, p. 334, 1882.

Large, terrestrial or amphibious vertebrata; skull bones deeply marked with pits and grooves which take the form of lateral-line canals; infra- and supraorbital canals, antorbital commissure, jugal canal, and occipital cross-commissure of the lateral-line system present in Eryops megacephalus Cope; carpus and tarsus osseous; pubis an osseous plate, surrounded in life by a large amount of cartilage; fore and hind limbs pentadactyl; orbits, in the typical genus, located far back on the skull and near the median line; cleithrum present on the scapula; vertebræ rachitomous, the intercentrum supporting the arch in the dorsal region; parasphenoid well-developed or reduced; teeth on pterygoids, palatines, prevomers, and parasphenoid.

Range: Upper Pennsylvanian to Permian.

Distribution: America, Europe, Asia.

Genus ERYOPS Cope, 1877.

Type: Eryops megacephalus Cope.

Skull long, comparatively narrow; proportion of length to breadth about 9 to 7. Roof bones coarsely sculptured posteriorly, finely sculptured anteriorly. Nasals and premaxillæ very large; frontals excluded from the orbits by junction of pre- and post-frontals. Pterygoids not meeting in the median line; parasphenoid dagger-shaped, tapering gradually to a point just in front of the palatine foramen; prevomers large. Orbits subcircular, situated in the posterior half of the skull; nares subovate, remote, at a considerable distance from the tip of the skull. Many minute denticles, on pterygoids, palatines, prevomers, and parasphenoid. Teeth circular in cross-section, strongly ribbed near the base, dentine strongly infolded. Three large teeth on each palatine. Mandible without postcotyloid process. Vertebræ rachitomous. Ribs double-headed. Pubis osseous. Three species (Permian), E. megacephalus, E. latus, and E. willistoni, are assigned to the genus.