EXTINCT BATRACHIA. 405 



the maxillaries do not exhibit any curvature, and the snout was doubt- 

 less acuminate. The orbits are long and narrowed in front. The teeth 

 are like those described in the last specimen, rather long, straight, acute, 

 and striate at the base. A section shows the enamel to be deeply in- 

 flected. The only inequality in their length is the slightly diminished 

 size posteriorly. 



This is one of the larger species of the Linton beds. In none of the 

 specimens are the thoracic scuta preserved. 



Width behind, .067 m. ; width between epiotics, .033 ; width at anterior 

 angle of orbits, .040; width of interorbital region, .013; length from epi- 

 otic to orbit, .025; length of orbit, .027; width of orbit, .013; length of 

 a maxillary tooth, .004; diameter of do. at base, .002. 



CoLOSTEUS, Cope. 



Trans. Amer. Philos. Soc, 1869, p. 22. 



This genus was proposed for Ganocephala, allied to Archegosaurus, but 

 differing as follows : 



There are no traops of vertebral, centra or spines, or of ribs, in portions 

 of six individuals preserved. No sclerotic bones can be found in one 

 cranium partially preserved. There appear to be two pairs of very 

 short limbs. The usual three sculptured pectoral bones are present, con- 

 sisting of a rhombic medial, and a pair of half rhomboid laterals. The 

 abdominal region is protected by a series of scales which extend 

 obliquely forwards to the medial line, where they meet, forming chev- 

 rons. They are closely approximated, and are composed of rhomboidal 

 scales which have a convex external and internal face, in transverse 

 section, and which overlap at the extremities, and are in contact by faces 

 which are oblique in both the longitudinal and transverse directions. 



The exact form of the muzzle can not be made out. It is, however, not 

 elongate, nor yet of the broad rounded form of Pelion. Several teeth are 

 preserved. There are two kinds, which occupy the margins of the max- 

 illary and dentary bones. The anterior teeth appear to be longer than 

 the posterior, though the latter are mostly broken off. Most of the teeth 

 are coarsely incised sulcate for perhaps their basal half Two long teeth 

 behind the distal extremity of the dentary are, on the other hand, very 

 finely and sharply striate for their basal half; the tip is sub-cylindric, 

 and very prolonged and acute. A small, dagger-shaped tooth near the 

 base of one of the posterior may belong to the successional, or to a small 

 outer series. A series of four elevated tooth bases, with a broken crown, 



