Osteology o/'Caturus and Osteoracliis. 383 



Dentition. 



The teeth are all simple hollow cones, and tlie internal 

 cavity in the fossil is usnally filled with calcite. They are 

 rounded in section, without any longitudinal keels, and the 

 slender apical portion alone is enamelled. The apex is more 

 or less curved and usually marked only with very delicate 

 stria3, though one splenial tooth is crimped in the lower part 

 of the enamel. The smooth brown base seems to have had a 

 relativelv thin wall in the larsrer teeth, iudging from fractures 

 by crushing, and one of the supposed palatine teeth shows a 

 natural indent of its outer face at the attached end. All the 

 teeth are fixed in shallow depressions and fused with the 

 supporting bone, and the only complete tooth of the maxillary 

 series seems to be worn (during the life of the animal) at the 

 apex. No successional teeth are observable. 



Axial Skeleton of Trunk. 



The vertebral column is represented by 12 of the pleuro- 

 centra, 15 of the hypocentra, and a few fragments of the 

 arches. As already mentioned, one pleurocentrum [pl.c), 

 one hypocentrum (^.c), and one neural-arch-shaped fragment 

 [n.) are crushed in the matrix at the occiput ; the others are 

 all detached. A typical pleurocentrum is shown of two thirds 

 the natural size in end view and from the superior and lateral 

 aspects in PI. XI. figs. 4, 4 a, 4 J. 



All the specimens are crushed and some much distorted, 

 but that here represented seems to retain approximately its 

 original form. It is not quite bilaterally symmetrical, one 

 side being longer than the other, and in this respect it differs 

 from the remainder of the series, which have a more regular 

 figure. In end view five distinct facettes are observed. Be- 

 tween the two branches of the bone there is the smooth 

 saddle- shaped surface {not.^ which would be directly in 

 contact with the persistent notochord ; above this is a pair of 

 small ovoid facettes of finely granulated aspect («.«,), to 

 support the basal segment of the neural arch, and each diver- 

 gent branch bears a great rugose flattened surface, which 

 would be apposed to the corresponding surface of the hypo- 

 centrum. "When viewed from above (fig. 4 a) the pair of 

 facettes for the support of the neural arcli is seen to occur on 

 both ends of the bone, with a small intervening space, this 

 indicating that the arches alternated with the vertebral bodies 

 as in Amia. It is also noteworthy that a conspicuous little 

 boss of variable development projects from the restricted area 

 between each pair of these neural facettes. In side view (lig. 4 b) 



