EXTINCT BATEACHIA. 401 



that it forms an irregular crescent. It supports two teeth, of which the 

 anterior is the larger, but there were, perhaps, others in advance, as the 

 alveolar border is imperfect towards the end of the muzz e. The ante- 

 rior two teeth of the maxillary bone are followed by a strong groove 

 which rises towards the side of the muzzle. At first sight this gives the 

 impression of the maxillo-premaxillary suture, and makes it appear 

 that both premaxillary bones are preserved, and that the foramen above 

 described separates the premaxillary spines, instead of representing the 

 external nostril. The cutting edges of the teeth of these bones have, 

 however, one direction, whence they represent one side of the cranium 

 only ; were both sides represented, the directions of the tooth axes would 

 be reversed. 



The premaxillary and maxillary teeth exhibit a cutting edge on the 

 outer posterior margin of the distal half; the base of the crown is sub- 

 round in section. The line-like grooves are distinct but not numerous, 

 their intervals measuring .75 mm. Beyond them the enamel is smooth. 

 The second maxillary tooth is larger than the first, which is equal to the 

 last premaxillary. The third and fourth maxillaries are equal to the 

 second, but the fifth is larger and longer, exceeding all the others. The 

 teeth of the dentary bone differ from those of the upper jaw in having 

 the cutting edge of the crown on the anterior aspect, while the posterior 

 border is obtuse. There is an obtuse cutting edge on the posterior mar- 

 gin of the anterior mandibular teeth. 



This description is derived from an adult animal, as the maxillary- 

 teeth in some instances are partially worn away by friction on their an- 

 terior and outer faces. 



Length of maxillary bone preserved, .146 m. ; length of do. supporting 

 five teeth, .073 ; length of first maxillary tooth, 15 ; diameter of do. at 

 base, .006; do. of second at base, .008; do. of fifth at base, .010; length 

 of basis of fifteen teeth of dentary, .145; length of ninth tooth, .020; 

 diameter at base of do., .008. 



The Leptophractus was about as large as an adult alligator, and ex- 

 ceeded in size any of the other species here described. 



EURYTHORAX, Cope. 



Established on a large thoracic shield of peculiar form. It is a median,. 



and exhibits on its outer or lateral borders broad, smooth surfaces for 



the contact of the overlapping margins of the lateral plates. The form 



is subround, with a large excavation from the posterior margin on each. 



26 



