22 THE EXTINCT BATRACHIA, REPTILIA 



GJVOCEPIIAIv/l. 



COLOSTEUS, Cope. 



This genus is proposed for Ganocephala, allied to Apateon ( Ardiegosaurus ) but differ- 

 ing as follows : 



There are no traces of vertebral centra or spines, or of ribs, in portions of six individ- 

 uals preserved. No sclerotic bones can be found in one cranium partially preserved. 

 There appears to be two pairs of very short limbs. The usual three sculptured pectoral 

 bones are present, consisting of a rhombic medial, and a pair of half rhomboid laterals. 

 The abdominal region is protected by series of scales which extend obliquely forwards to 

 the medial line, where they meet, forming chevrons. 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 cannot 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 maxillary 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 their distal extremity of the dentale, are on the other hand very 

 finely and sharply striate for their basal half; the tip is subcylindric, and very prolonged 

 and acute. A small, dagger-shaped tooth near the base of one of the posterior, may be- 

 long to the successional, or to a small outer series. A series, of four elevated tooth bases, 

 with a broken crown, of much smaller size than those of the jaws belongs to the vomerine 

 or a palatine series. The row is single and uniform. 



The superior face of the cranium is injured, but the component bones appear to have 

 possessed a radiating sculpture of no great distinctness. 



The form of the body seems to have been long and fish-like, with little contraction near 

 the limbs. Caudal extremity is not preserved. There were probably two pairs of very 

 weak limbs, of which three metacarpals of the anterior are preserved. A narrow longi- 

 tudinal bone extends posteriorly from the lateral pectoral bone. Its extremity is broken, 

 but a flat, narrow, longitudinal bone, with a dilated extremity curved outwards, may be- 

 long to it, or be the humerus. I find no distinct traces of branchial arches. 



The affinities are thus obviously to Apateon, and it is not beyond possibility that future 

 investigations may prove it is the same, though this is not probable at present. 



Portions of seven individuals of one species, and of one individual of another, were 

 discovered by Prof. John S. Newberrv at Linton, Ohio. They differ as follows : 



