VEETEBEATES. 



203 



The teeth are so variable in relative dimensions that comparative 

 measurements are of little use for other purpose than to show the 

 maxima attained by the species, as indicated by the breadth; thus, 

 the largest perfect example shows a transverse diameter across the 

 posterior margin of 33 mm., the smallest perfect tooth measuring 

 about 16 mm. in breadth. 



A form differing from that above 

 noticed chiefly in the proportion- 

 ately greater length of the teeth, 

 compared to their breadth, giving 

 them a more lozenge-shaped outline 

 are quite as numerously represented 

 in the collections, and which we sup- 

 pose to have constituted the arm- 

 ature of the opposite jaw of the 

 same species. Examples of much- 

 worn, mature teeth present an 

 almost regular arch, or curvature, 

 from the inner anterior to the outer 

 posterior spur angle without dis- 

 tinct intermediate angulation at the 

 junction of the exterior border with 

 the anterior margin, and the inner 

 coronal prominence, as also the 

 outer lesser ridge, is reduced to a 

 nearly plane surface transversely. 

 The inner articular border is quite 

 straight, extremely thickened and 

 series". ngitudinal proflles of maxillary wedging out towards the exterior 

 border; in every instance of the teeth here admitted, the truncated 

 facet is extremely small, sometimes occurring at one angle, again at 

 the opposite ; however, most of the specimens being truncated at the 

 posterior angle. The very gentle longitudinal convexity of the coronal 

 surface of the tooth indicate that the curvature of the series constituted 

 a smaller segment of a circle than was the case with the before- 

 mentioned form; hence the supposition of their maxillary position. 

 In dimensions, as also in surface structure, the form agrees with 

 that previously noticed. 



Diagram of maxillary teeth of Psammo- 

 dus Springeri. 



a. Maxillary series, triturating surface. 



b. Transverse profile of maxillary se- 

 ries. 



