34 FOSSIL REPTILIA OF THE 



such teeth, the mode of attachment being by partial anchylosis to the bottom of 

 an alveolar groove and to the side of an outer alveolar wall. 



The crown of the teeth is broad, compressed, with sharp, subcrenate margins 

 at the apical half, curving in most to a low point at the summit, and having a 

 semicircular contour when this is worn away, as at c, fig. 10. A few of the 

 anterior teeth are narrower, and the crenate margins converge, almost straight, to 

 a sharper point, as in a, fig. 10. The older teeth have the crown reduced by 

 attrition to the shape of a spade [b, fig. 10), suggesting the name of the genus. 

 The enamel is marked by very fine, longitudinal ridges, the terminations of which 

 give the crenate character to the unworn margins of the crown ; a larger longi- 

 tudinal rising marks the middle of the flattened surface, and is more conspicuous 

 on the outer than the inner side of the crown in the lower jaw ; it commences at 

 a short distance from the base of the enamelled crown, and terminates at the 

 apex. From this middle, thickest part of the crown the tooth narrows to the 

 lateral margins, its transverse section across the middle of the crown resembling 

 that of the upper part of the crown of the tooth oi Echinodon (fig. 6, b)- 



In a portion of the upper maxillary bone of Macellodon Brodiei, the low 

 palatal alveolar plate terminates internally in a smooth border, which had formed 

 the outer boundary of an extended palatal vacuity, as in most lizards ; this struc- 

 ture, with the unequal development, the succession, and pleurodont mode of 

 implantation of the teeth, indicates the Lacertian affinities of Macellodon. 



In a small slab from the lower part of the Purbeck stratum, called " dirt-bed, 

 containing shells," Mr. Brodie discovered the dentary element of the lower jaw 

 of Macellodon, containing thirteen teeth, and alveolar depressions for twenty ; 

 with this were associated the neural arch of a vertebra, portions of ribs, and 

 some dermal, bony scutes. The teeth in place were anchylosed to depressions 

 in an outer alveolar wall ; a few at the fore part of the jaw were less expanded 

 relatively to their length than the rest, which presented the Macellodont type of 

 crown. They are separated by slight intervals, and the teeth are much smaller in 

 proportion to the jaw than in Nuthetes. The dentary bone, figured of the natural 

 size at Tab. VIII, fig. 10, presented the posterior notch for articulation with the 

 angular and surangular elements ; its outer surface is convex, and perforated at 

 its anterior half by a linear series of nervo-vascular canals. 



The neural arch associated with the above portion of lower jaw bears a 

 greater proportional size thereto than in most lizards ; it exhibits long diapo- 

 physes, as in the lumbar and anterior caudal Saurian vertebrae, supports a 

 moderately long spine, and shows a small, circular, neural canal ; the zygapophyses 

 have been broken away from the exposed surface ; and the centrum has been, 

 apparently, detached from a sutural connexion with the arch, which would be 

 rather a Crocodilian than a Lacertian character. 



